GUINEA PIGS Infectious Diseases by lpd48805

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                                          GUINEA PIGS:
                                       Infectious Diseases


                                   Donna J. Clemons, DVM, MS

                                      Lizabeth A. Terril, DVM

                                Joseph E. Wagner, DVM, MPH, PhD

                                Department of Veterinary Pathology
                                  College of Veterinary Medicine
                                       University of Missouri
                                        Columbia, Missouri

   The Laboratory Animal Medicine and Science - Series ll - has been developed by the Autotutorial
 Committee of the American College of Laboratory Animal Medicine (ACLAM): C. W. McPherson, DVM,
 Chair; J. E. Harkness, DVM;J. F. Harwell, Jr., DVM; J. M. Linn, DVM; A. F. Moreland, DVM; G. L. Van
 Hoosier, Jr., DVM; L. Dahm, MS. Instructional development and production assistance provided by L.
Dahm, MS, and B. J. McGough, BS Medical Comm. The development of these programs is supported by
    a grant from the US Department of Agriculture: National Agricultural Library grant 59-32U4-9-45

                     Laboratory Animal Medicine and Science - Series II
                                    is produced by the
                     Health Sciences Center for Educational Resources
                                 University of Washington.
2                                       LABORATORY ANIMAL MEDICINE AND SCIENCE - SERIES II

PRIMARY AUDIENCE          Veterinary students and graduate veterinarians studying laboratory
animal diseases.

SECONDARY AUDIENCE        Investigators using laboratory guinea pigs, research technicians,
                          veterinary technicians, and laboratory animal technicians.

GOAL                      To provide the viewer with an understanding of the causes, frequency of
                          occurrence, clinical and pathologic signs, diagnosis, treatment and
                          prevention, control, and significance of infectious diseases of guinea

OBJECTIVES           Given a guinea pig or a description of a guinea pig assumed to be diseased,
                     you should be able to state:

                     1.    possible common infectious diseases based on the signs.

                     2.    probable etiologic agent.

                     3.    possible means of transmission.

                     4.    expected clinical and pathologic signs.

                     5.    methods for confirming the diagnosis.

                     6.    recommendations for treatment, control and prevention.

                     7.    significance of the disease.
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1. Series                  Laboratory Animal Medicine and Sciences - Series ll

2. Program title          Guinea Pigs: Infectious Diseases

                          This autotutorial session provides an overview of the more common infectious
                          diseases of the guinea pig. It was designed to assist in teaching basic
                          information about infectious diseases of guinea pigs to veterinary students,
                          technicians and other biomedical science students.

                          Clinical syndromes, gross and histopathologic lesions, as well as methods of
                          diagnosis, treatment and control of the more significant infectious diseases of
                          guinea pigs are examined.

3. Objectives             Given a guinea pig or a description of a guinea pig assumed to be diseased,
                          you should be able to state:

                          •   possible common infectious diseases based on the signs.
                          •   probable etiologic agent.
                          •   possible means of transmission.
                          •   expected clinical and pathologic signs.
                          •   methods for confirming the diagnosis.
                          •   recommendations for treatment, control and prevention.
                          •   significance of the disease.

4. Overview               In this program, we will address the various types of infectious disease in
                          guinea pigs, including:

                          •   bacterial
                          •   fungal
                          •   viral
                          •   chlamydial
                          •   parasitic

5. Section title          BACTERIAL AND FUNGAL DISEASES

                          Bacterial and fungal agents are responsible for some of the most significant
                          diseases of guinea pigs.

6. Bacterial diseases     Several primary respiratory diseases of the guinea pig are of bacterial origin,
                          with Bordetella bronchiseptica and Streptococcus pneumoniae being the most
                          important. Other infectious agents listed on this image act as opportunistic
                          invaders in traumatized tissue (Streptococcus zooepidemicus), and contribute
                          to enteric disease (Clostridium piliforme and Salmonella spp) and dermatitis
                          (Trichophyton mentagrophytes).
4                                           LABORATORY ANIMAL MEDICINE AND SCIENCE - SERIES II

7. Pneumonic lung

                                        Pneumonic lungs, seen here as the dark-colored tissue, may
                                        have one or more areas of consolidation and hemorrhage.
                                        Bordetella bronchiseptica, Streptococcus pneumoniae, or other
                                        bacteria frequently cause pneumonia in guinea pigs. Affected
                                        animals may have no clinical signs, or exhibit nasal discharge,
                                        sneezing, dyspnea, weight loss, or sudden death. Increased
                                        incidence of abortion and stillbirths may accompany respiratory
                                        signs in epizootics.

8. Bordetella         Bordetella bronchiseptica is a small gram negative rod. Incidence of Bordetella
                      bronchiseptica infection in guinea pigs may be high because many animal
                      species such as rabbits, dogs and cats carry the organism in nonclinical
                      infections. For this reason, rabbits and guinea pigs should not be housed
                      together. Transmission between animals is by direct contact, aerosol, or
                      contaminated fomites. Asymptomatic carriers frequently occur.

9. Bronchopneumonia

                                      Lesions include rhinitis, tracheitis and pulmonary consolidation.
                                      Typical histopathologic lesions of purulent bronchitis and
                                      bronchopneumonia with large accumulations of neutrophils and
                                      intraluminal debris (arrow) are shown here.

10. Head tilt

                                      Otitis media may also occur with Bordetella infections. Severe
                                      otitis media may be accompanied by head tilt (torticollis).
V-9025 - GUINEA PIGS: Infectious Diseases                                                                    3

11. Radiograph

                                             One may detect suppurative otitis media through radiographic
                                             examination of the tympanic bulla, as illustrated in this
                                             unilaterally affected animal (arrow). Otitis also may be
                                             detected as cloudiness in the tympanic membrane visualized
                                             with an otoscope. Diagnosis of bordetellosis is based on
                                             clinical signs, histopathologic lesions and recovery of the
                                             organism from the respiratory exudate. Pearl-like colonies
                                             grown on blood agar reach maximal size in 72 hours.

12. Bordetella

                                     Treatment of Bordetella bronchiseptica infection is often unrewarding.
                                     Antibiotics of choice include chloramphenicol, sulfamethazine and
                                     trimethoprim-sulfa. Autogenous or commercial bacterins may be
                                     used to prevent overt disease but may not prevent the carrier state.
                                     Effective prevention includes good husbandry and maintenance of a
                                     closed Bordetella free colony. Guinea pigs carrying the organism are
                                     generally not suitable for research because of the tendency to break
                                     with clinical disease when stressed.

13. Antibiotic toxicity   Antibiotics may suppress clinical signs but usually do not eliminate the organism
                          and fatal antibiotic-induced enterocolitis is always a concern in treating guinea
                          Antibiotics implicated include penicillin, aminoglycoside, erythromycin,
                          clindamycin, lincomycin, chlonetracycline, oxytetracycline, bacitracin, and

14. S. pneumoniae

                                            Fibrinopurulent pericarditis, shown here, can be caused by
                                            Streptococcus pneumoniae. It may be accompanied by fibrinous
                                            pleuritis and bronchopneumonia. Streptococcus pneumoniae is
                                            an alpha-hemolytic, gram positive coccus that tends to occur in
                                            pairs. Mortality is high in enzootics. Clinical signs are similar to
                                            those seen in other bacterial pneumonias. Otitis media, metritis
                                            and other suppurative processes may occur. Transmission of
                                            Streptococcus pneumoniae is by aerosol or direct contact with
                                            diseased or asymptomatic carrier guinea pigs, rats or humans.

15. Recovering strep

                       Streptococcus pneumoniae may be recovered by culture of
                       affected tissues on blood agar incubated in 10% C0 at 37° C.
                       Identification of the organism is confirmed by the appearance
                       of a distinct zone of growth inhibition around an
                       optochinimpregnated disk on a blood agar plate. Diagnosis
                       also may be made by examining the stained smears of exudate
                       for pairs and chains of gram positive cocci. Treatment may be
                       approached the same as for Bordetella infections. Control
                       involves good husbandry, stress reduction and elimination of
                       carriers from the colony.

                       Although no cases of transmission from laboratory animals to
                       human have been documented, it should be noted that
                       Streptococcus pneumoniae can cause respiratory and
                       meningeal disease in humans, particularly in elderly and
                       immunocompromised persons.

16. Lymphadenitis

                       Cervical lymphadenitis is caused most commonly by
                       Streptococcus zooepidemicus. Other Streptococcus spp and
                       Streptobacillus moniliformis are rarely implicated. The
                       organism may be an asymptomatic inhabitant of the upper
                       respiratory track that opportunistically invades damaged
                       mucosa. Bite wounds or aerosol spread onto mucosal
                       surfaces are the primary modes of transmission. Cervical
                       lymph nodes become swollen, abscess and often rupture.

17. Lymph node

                       Lymph nodes progress to encapsulated abscesses filled with
                       yellow-white purulent exudate. Diagnosis is based on clinical
                       signs and culture of the organism from lesions. Treatment may
                       include drainage and lavage of lesions and antibiotic therapy
                       with chloramphenicol or trimethoprim-sulfa. Control is
                       accomplished by culling affected animals prior to rupture of
                       lesions and separating new stock from an existing colony.
                       Killed bacterins are not effective in preventing disease, but
                       scratch inoculation of the oral mucosa with Streptococcus
                       zooepidemicus recovered from swine stimulates immunity.
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18. Infected liver

                                             This image shows the multiple gray-white foci often found in
                                             the liver of guinea pigs with Tyzzer's disease. Overt disease is
                                             characterized by a rough coat, lethargy, watery diarrhea and
                                             death. Necropsy examination may reveal lesions in the
                                             intestine, including edema, hemorrhage, ulceration and fluid
                                             contents. The liver may be enlarged.

19. C. piliforme          The causative agent, Clostridium piliforme is a gram negative, PAS-stain
                          positive, spore forming, obligate intracellular rod. Infection occurs by fecal-oral
                          transmission of spores that may persist for years in the environment. The
                          prevalence of Tyzzer's disease in guinea pig populations is not known. Carriers
                          of the disease are probably widespread, but overt disease is typically seen only
                          in immunocompromised or stressed individuals.

20. C. piliforme

                                            Inflammatory infiltration is apparent in the lamina propria of the
                                            intestine (on the left) and frequently in the liver (on the right).

21. Intestine and liver

                                             Definitive diagnosis is made by identifying 'pick-up sticks'
                                             arrangements of organisms in Giemsa or Warthin-Starry silver
                                             stained tissues (as seen here at the arrows), serologic testing
                                             for antibody to Clostridium piliforme, or inoculating weanling
                                             gerbils with feces from affected animals. Gerbils are very
                                             sensitive to Clostridium piliforme and rapidly develop illness
                                             and diarrhea, as well as the typical hepatic lesions associated
                                             with Tyzzer's disease. Treatment may be attempted, but is
                                             usually unrewarding. Suppression of signs is sometimes
                                             accomplished with chloramphenicol. Outbreaks can be
                                             controlled by strict sanitation, appropriate cleaning of the
                                             environment and reducing environmental stress.
8                                                LABORATORY ANIMAL MEDICINE AND SCIENCE - SERIES II

22. Salmonella

                                             Salmonella typhimurium and other Salmonella spp will infect
                                             guinea pigs. Sporadic outbreaks with high mortality are the
                                             rule, with guinea pigs becoming most susceptible around
                                             parturition, weaning, or other times of physiologic stress.
                                             Clinical signs of salmonellosis include anorexia, rough haircoat,
                                             lethargy, weight loss, soft feces, reproductive inefficiency and

23. Transmission            Many animal species harbor Salmonella organisms which are shed intermittently
                            in the feces. Transmission is fecal-oral; organisms often are introduced in
                            contaminated foods such as fresh fruits and vegetables, or through the water

24. Fluid filled GI tract

                                              Necropsy findings may include gas and fluid contents in the
                                              gastrointestinal tract as seen here. Enlargement of the liver,
                                              spleen and lymphoid tissues may also be found.

25. Spleen

                                             Necrotic foci may be found throughout the spleen, liver and
                                             lymphatic tissues. Clinical signs, necropsy findings and
                                             histopathologic lesions suggest a diagnosis of salmonellosis.
                                             Confirm the diagnosis by culture of feces and lesioned lymph
                                             nodes in enrichment broth and selective media. Treatment is
                                             not generally recommended, because the carrier state may be
V-9025 - GUINEA PIGS: Infectious Diseases                                                                 3

26. Management             Culture-positive animals should be removed from the colony. The room and
equipment should be disinfected and restocked with clean animals. This approach risks failure to detect
all carriers by culture and subsequent reappearance of disease. In some cases complete eradication
followed by disinfection and restocking may be necessary. To avoid an outbreak, rigid sanitation and
quarantine procedures should be observed and new arrivals and human caretakers screened.
Salmonella spp are infective to humans and may cause serious disease in children and
immunocompromised individuals.

27. Dermatophytosis

                                            This animal has dermatophytosis and may also show some
                                            signs of barbering. Trichophyton mentagrophytes is the most
                                            common cause of dermatophytosis (ringworm) in the guinea
                                            pig and rabbit. While clinical infections are uncommon,
                                            asymptomatic carriers are abundant. Spores may be found in
                                            hair, bedding and soil. Animals become susceptible when
                                            stressed and may develop irregular alopecia with occasional
                                            crusting over the dorsal body surface.

28. Fungal spores

                                            Microscopic examination of a skin scraping or histologic skin
                                            sections may reveal fungal spores (as seen here) and hyphae.
                                            (A few drops of potassium hydroxide (KOH) may help clear the
                                            image of unwanted debris.) Culture of hair shafts from a lesion
                                            onto dermatophyte test media may also be used to confirm a
                                            diagnosis. Topical antifungal creams used daily for 2 to 4
                                            weeks, or griseofulvin at 25 mg/kg daily in the water for 14
                                            days or 20mg/kg in feed for 25 days, are generally effective
                                            treatments. Prevention of outbreaks may be accomplished by
                                            strict sanitation, screening suspect animals and culling affected
                                            animals. Trichophyton mentagrophytes is infective to humans
                                            and other animal species.

29. Mastitis

                                            Mastitis is common in lactating sows. Milk provides an
                                            excellent media for the growth of bacteria that may invade
                                            when young traumatize the teats. Multiple agents have been
                                            implicated, including Pasteurella spp, Klebsiella spp,
                                            Staphylococcus spp, Streptococcus spp and others. Mammary
                                            glands become warm, enlarged and hyperemic, as illustrated
                                            on the image. The milk may appear bloody; depression and
                                            even death may follow. Diagnosis is based on clinical signs.
                                             Treatment includes hot packs and antibiotic therapy. Surgical
                                             resection of the affected tissue may need to be considered if it
                                             becomes necrotic or gangrenous. Young should be weaned
                                             immediately. The best prevention for mastitis involves proper
                                             sanitation and maintenance of a clean environment for
                                             lactating sows.
10                                             LABORATORY ANIMAL MEDICINE AND SCIENCE - SERIES II


                        Some viral and chlamydial disease agents are listed on this image, but they are
                        of limited importance. Few if any clinical signs are seen, yet researchers should
                        be aware that studies may be complicated by the presence of subclinical

31. Conjunctivitis

                                          Overt signs of inclusion body conjunctivitis, as seen in this
                                          image, are found primarily in one to three week old guinea
                                          pigs. Spontaneous resolution of the disease is complete by
                                          four weeks of age in most animals. Chlamidia psittaci, the
                                          infective agent, is transmitted via feces, saliva and nasal
                                          secretions; infections may be spread by direct contact or
                                          aerosol. The disease is enzootic in many guinea pig colonies.
                                          Erythematous conjunctiva, serous ocular discharge and
                                          photophobia are found in affected animals.

32. Conjunctival scraping

                                        Definitive diagnosis is made from microscopic examination of
                                        scrapings of the conjunctival mucosa, shown here, and
                                        identification of cytoplasmic inclusion bodies (arrow) in epithelial
                                        cells. Serologic screening by fluorescent antibody test is also
                                        available. Most cases resolve without treatment, but ophthalmic
                                        ointments may be used to make the animal more comfortable
                                        during the acute phase of disease. No cases of human
                                        chlamydial infection have been attributed to guinea pigs, yet this
                                        organism should still be considered a potential human pathogen.

33. Salivary gland

                                        Cytomegalovirus is a common, mostly subclinical, pathogen of
                                        guinea pigs. Immunosuppressed and stressed animals will
                                        sometimes exhibit overt signs such as swelling of the salivary
                                        glands and tenderness in the affected region. The agent, a
                                        herpes virus, resides in the nerve cell bodies of the trigeminal
                                        nerve and replicates in the salivary gland ductal epithelium
                                        during times of stress. Transmission occurs through shedding of
                                        the virus in saliva and, possibly, transplacentally.
                                        Cytomegalovirus trophism for placental tissues also leads to late
                                        gestational abortion due to placental necrosis. Diagnosis is
                                        made by histopathologic examination of submaxillary salivary
                                        gland for periductal lymphoid aggregates, large eosinophilic
                                        intranuclear inclusion bodies (large arrow) and very small
                                        intracytoplasmic inclusion bodies (small arrow). Indirect
                                        fluorescent antibody serologic testing is available. No treatment
                                        other than stress reduction is usually attempted. Virus research
                                        and reproductive studies may be complicated by this disease.
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34. LCM                   Lymphocytic choriomeningitis (LCM) is caused by an RNA Arenavirus. No
                          naturally occurring cases have been reported in guinea pigs. However, guinea
                          pigs inoculated with contaminated biologicals have contracted the disease. Wild
                          mice are the natural reservoir; they shed virus in saliva and urine that may infect
                          other rodent species via direct contact, aerosol spread, fomites, or mechanical

35. Posterior paralysis

                                            Usually there are no clinical signs, but rear limb paralysis and
                                            CNS disturbances from meningitis have been reported in guinea
                                            pigs with LCM. Necropsy examination may reveal liver and
                                            spleen enlargement, while histopathologic examination reveals
                                            lymphoid infiltrates around meningeal blood vessels and
                                            glomerulonephrosis. Diagnosis should be confirmed by ELISA
                                            and IFA serologic screening; mouse antibody production (MAP)
                                            testing may also be done. Eradication of the virus from an
                                            infected colony is complicated by intrauterine transmission; the
                                            entire colony should be euthanatized. Introduction of the virus
                                            into a colony can be prevented by screening colonies with
                                            serologic tests and eliminating access of wild animal vectors.
                                            Tumors and other biologic materials to be introduced into guinea
                                            pigs should be screened for LCM. LCM is capable of causing
                                             mild to severe illness in humans.

36. Lymphosarcoma

                                             A type C Oncornavirus is the etiologic agent responsible for the
                                             leukemia found in aged guinea pigs. Cavian leukemia virus is
                                             widespread and usually transmitted transplacentally, remaining
                                             dormant in the animal until aging or stress trigger disease
                                             expression. Lymphadenopathy, rough hair coat and ascending
                                             paralysis are associated with the clinical disease syndrome.

37. Hepatomegaly

                                             Hepatomegaly, splenomegaly and diffuse lymphadenopathy
                                             are found frequently in guinea pigs with viral-induced leukemia/
                                             lymphosarcoma. Enlarged organs appear mottled and light in
                                             color. Anemia and leukocytosis are often present.
12                                                LABORATORY ANIMAL MEDICINE AND SCIENCE - SERIES II

38. Lymphoid infiltration Microscopic examination of these lesioned organs reveals the presence of
                          lymphoblastic cellular infiltrates obliterating the architecture of tissues. Diagnosis
                          can be made in a living animal by examining a peripheral blood smear for
                          disproportionately large numbers of lymphoblasts. No treatment or preventive
                          measures are recommended.

39. Other viral agents    Positive titers to Sendai virus, pneumonia virus of mice (PVM) and simian virus 5
                          (SV 5) are frequently detected in apparently healthy guinea pigs. These
                          Paramyxoviruses have the ability to briefly replicate in the guinea pig, allowing it
                          to become a potential reservoir of virus for murid rodent species. Colony
                          contamination and potential research interference is reduced by maintaining strict
                          separation of animal species.

40. Adenovirus            Although incidence is low in the United States, cavian Adenovirus should not be
                          overlooked. Pneumonia with a high rate of morbidity is associated with this virus
                          in other areas of the world. Serologic testing for Adenovirus is not available in
                          the U.S., but a presumptive diagnosis may be made based on the presence of
                          basophilic intranuclear inclusion bodies within respiratory epithelial cells of
                          animals with pneumonia or necrotizing tracheitis.

41. Coronavirus           A Coronavirus-like virion has been found in enteric tissues of young guinea pigs
                          with acute wasting and diarrhea syndrome. Enteric Coronavirus infection is
                          associated with acute and often serious disease in young rabbits, pigs, dogs,
                          cats and cattle. It may prove to be a significant disease in guinea pigs as well.

42. Section title         PARASITES

                          Many parasites are known to infect guinea pigs, but as a rule, parasites are more
                          a problem in hobby and breeding colonies than in the research setting. In this
                          program, we present information on the major ectoparasites, protozoans and

43. Ectoparasites         Common ectoparasites of the guinea pig include the mites Trixicaris caviae and
                          Chirodiscoides caviae, as sell as the lice, Gliricola porcelli and Gyropus ovalis.

44. Alopecia

                                           Acariasis in guinea pigs is primarily associated with two species
                                           of mite, Trixacaris caviae and Chirodiscoides caviae. Both mites
                                           are found in greater frequency in pet and breeding colonies than
                                           in research colonies. Mild to severe alopecia may be seen, as
                                           illustrated in the image. Trixacaris caviae, a burrowing mite,
                                           poses a significant threat to the health of a guinea pig colony.
                                           Infestations can interfere with research by affecting the general
                                           health and well-being of the animals and by providing vectors for
                                           other infectious diseases. Trixicaris caviae tend to distribute on
                                           the neck, shoulders, lower abdomen, and inner thighs, whereas
                                           Chirodiscoides caviae distribute more randomly.
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45. Trixacaris caviae

                                             Trixacaris caviae, a sarcoptid mange mite, burrows through the
                                             keratin layer of the epidermis causing alopecia, crusting, and an
                                             intense pruritus that may lead to self mutilation, debility and

46. Chirodiscoides caviae

                                              Chirodiscoides caviae, a fur mite, may cause few or no clinical
                                              signs in infested animals. Mites are transmitted by direct
                                              contact with the host, animal bedding, or hair and debris.

47. Mite in keratin layer

                                             Antemortem diagnosis is made by preparing skin scrapings with
                                             IO% KOH and identifying the mites microscopically (as illustrated
                                             in the previous two images) or by examining the fur with a
                                             magnifying glass. Trixacaris caviae may be identified
                                             postmortem in the keratin layer of sections of the skin. Pelts
                                             may be placed on a dark background and examined with a
                                             dissecting microscope for fur mite migration.

48. Treatments              Reported treatments for acariasis include pyrethroid flea powder dusts, lime
                            sulfur dips and injections with ivermectin. While the safety and efficacy of
                            ivermectin in guinea pigs for external parasite control has not been established in
                            controlled studies, it has been anecdotally reported to be effective in guinea pigs.
                            Colony outbreaks can be prevented by placing clean animals into a clean
                            environment and eliminating contamination by wild rodents. In the event of an
                            outbreak, infected animals should be separated and treated while the premises
                            are thoroughly cleaned. Allow the area to remain empty for 3 weeks before
                            reintroducing animals, in order to ensure the death of any mites remaining in the
14                                        LABORATORY ANIMAL MEDICINE AND SCIENCE - SERIES II

49. Lice

                                      Guinea pig lice, Gliricola porcelli (left) and Gyropus ovalis
                                      (right) are chewing lice that cause occasional alopecia and mild
                                      pruritus with heavy infestations; Gliricola porcelli is seen more
                                      commonly. Lice are spread by direct contact with the host or
                                      contaminated bedding.

50. Lice and nits

                                      This image illustrates low power magnification via a dissecting
                                      Magnification of the pelt adjacent to lesions or around the neck
                                      will reveal nits attached to the hair shaft. Pelts may be cooled
                                      and examined for migration of the parasites toward the hair
                                      tips. Treatment is the same as that for mites. Rooms should
                                      be scrubbed and fumigated before restocking with clean
                                      animals. New arrivals should be quarantined and examined for
                                      lice prior to placement in existing colonies.

51. Protozoans      The protozoan Cryptosporidium sp is a major cause of enteric disease in guinea
                    pigs. Intestinal colonization may lead to lethargy, rough hair coat, weight loss
                    and diarrhea.

52. "Greasy Coat'

                                      Affected individuals often have a 'greasy" appearance, as
                                      illustrated by the matted hair along the midline in the
                                      accompanying image. Subclinical infection is common.
                                      Transmission occurs through ingestion of mature oocysts in
                                      contaminated food, water and fomites. Necropsy examination
                                      may reveal hyperemia of the small intestine, serosal edema of
                                      the cecum, watery ingesta and general emaciation in affected
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53. Intestine

                                            Cryptosporidium sp preferentially colonizes the anterior portion
                                            of the ileum, where fusion, atrophy and metaplasia of villous
                                            epithelium are seen. Eosinophilic infiltration of the lamina
                                            propria frequently accompanies other changes. Diagnosis may
                                            be confirmed by identification of the organism within epithelial
                                            cells (arrow). Mucosal scrapings or smears of fresh feces
                                            examined with phase contrast microscopy may be the best
                                            method of diagnosis; fecal flotation is generally unrewarding.

54. Management           No effective treatment for Cryptosporidium sp is available, but addition of 0.2%
                         sulfamethazine to the water supply may suppress outbreaks. Oocysts can be
                         destroyed by cleaning the environment with 5% ammonia. Prevention of the
                         disease is best approached by improving sanitation and avoiding contact of
                         guinea pigs with other susceptible species. Cryptosporidium sp is not species
                         specific and is potentially zoonotic to other animal species and humans.
55. Protozoans

                                            Balantidium caviae, a relatively nonpathogenic protozoan, is
                                            commonly found in fecal smears (left), or on histopathologic
                                            examination of the gastrointestinal tract. Eimeria caviae (right),
                                            is found in the colon and may cause overt clinical coccidiosis in
                                            infected colonies. Eimeria sp may be diagnosed antemortem by
                                            fecal flotation, or postmortem by colonic mucosal scrapings or
                                            histological examination of the colon.

56. Protozoans

                                             Tritrichomonas spp (left) and Giardia sp (right) also are
                                             frequently incidental findings. In this image, tritichomonads are
                                             found in large numbers in the lumen, along with ingesta and
                                             the larger Entamoeba organisms; Tritrichomonas spp are oval
                                             to pear-shaped structures that stain pink in this preparation.
                                             These organisms may contribute to occasional diarrhea in host
                                             animals. Episodes of diarrhea, if they occur, may be controlled
                                             with metronidazole at 30-60 mg/kg PO once daily for 5 days.
                                             Enteric protozoans are not typically species specific.
                                             Protozoans should be considered zoonotic agents with
                                             potential to infect humans.
16                                            LABORATORY ANIMAL MEDICINE AND SCIENCE - SERIES II

57. Klossiella cobaye

                                          A nonpathogenic renal coccidian, Klossiella cobaye, is viewed
                                          as an incidental finding in histopathic sections of kidney.
                                          Schizonts may be found in the epithelial cells of the renal

58. Paraspidodera

                                          The only nematode commonly associated with guinea pigs is
                                          the roundworm, Paraspidodera uncinata. Adult worms (left)
                                          dwell in the cecum and shed eggs (right) into the feces. Eggs
                                          are then ingested in contaminated food or water. Infections
                                          are usually considered insignificant. Typical thick-shelled,
                                          ascarid-like eggs are identified on fecal flotations. Piperazine
                                          has been reported to be an effective treatment. Ivermectin
                                           injected SC at 0.2 mg/kg may be used, but again, the safety
                                           and efficacy of this product in guinea pigs has not been
                                           established in controlled studies. Improving environmental
                                           sanitation and increasing the frequency of bedding changes
                                           helps to eliminate the parasite by reducing the spread of eggs
                                            to other animals and decreasing reinfection of treated animals.

59 .   ACLAM credits                    This program was developed for the American
                                        College of Laboratory Animal Medicine.
                                                  C. W. McPherson, DVM Chair
                                                      J. E. Harkness, DVM
                                                     J. F. Harwell, Jr., DVM
                                                         J. M. Linn, DVM
                                                      A. F. Moreland, DVM
                                                   G. L. Van Hoosier, Jr., DVM
                                                          L. Dahm, MS

                          Instructional development, editing and production management provided by L.
                           Dahm, MS, and Bob J. McGough, BS Medical Communication. Illustrations,
                                    graphics and imagery produced by Dale Leuthold, BA, and
                                                        Joseph Wilmhoff, BIS.
                                 Guide production by Pamela Young and Barbara Macfadden, BA.
                        The development of this program was supported by a grant from the Department
                                         of Agriculture: National Agricultural Library Grant 59-32U4-9-45

61.    HSCER credits                                   Produced by the
                                       Health Sciences Center for Educational Resources
                                                   University of Washington
                                                      Seattle WA 98195
V-9025 - GUINEA PIGS: Infectious Diseases                                                                3


Feldman, S. H., I. A. Richardson, and F. L. Clubb, Jr. 1990. Necrotizing viral bronchopneumonia in
guinea pigs.
Lab. Anim. Sci. 40: 82- 83.

Harkness, J. E., and J. E. Wagner. 1989. The biology of rabbits and rodents, 3rd ed. Lea and Febiger,

Jaax, G. P., N. K. Jaax, 1. P. Petrai, K. D. Corcoran, and A. P. Vogel. 1990. Coronavirus-like virions
associated with a wasting syndrome in guinea pigs. Lab. Anim. Sci. 40: 375-378.

Manning, P. J., J. E. Wagner, and J. E. Harkness. 1984. Biology and diseases of guinea pigs, p. 149-
182. In J. G. Fox, B. J. Cohen, and F. M. Loew (ed.), Laboratory animal medicine. Academic Press, Inc.,
Orlando, Fla.

Schnurrenberger, P. R., and W. T. Hubbert 1981. An outline of the zoonoses. The Iowa State Press,
Ames, Iowa.

Wolff, A., S. K. Shanker, C. L. Gibbs, Jr., and D. C. Gajdusek. Cervical lymphoblastic leukemia in an
aged guinea pig. Lab. Anim. Sci. 38: 83-84.


The authors express appreciation to the following individuals who contributed Kodachrome images to this


J. E. Wagner, College of Veterinary Medicine, University of Missouri.

Howard Wilson, University of Missouri, for assistance in photography and image preparation for this


Previous contributors to the ACLAM image series.

This project was supported in part by Grants RR 00471 and RR 07004 from the National Institutes of
Health, Bethesda Md.

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