Pollution - Pathogens by fqu18406


The number and prevalence of diseases found in the
  marine ecosystem is increasing at a rapid rate.

  The cause of this increase in not known and the
 pathways of disease spread is either not known or
                poorly understood.

Some diseases may have an anthropogenic source or
their effects made worse by anthropogenic activities
    e.g. global warming changing distributions,
        pollutants effecting immune systems
Researchers have
analyzed recent reports
of marine disease
(from 1970 – 2001 publications)
[Ward and Lafferty (2004)]
   Increases in Marine Disease Reports

• Disease reports had decreased in fish.
• No trends were noted for seagrasses, decapods
  or sharks/rays.
• Increases in disease reports were noted for
  turtles, corals, urchins and molluscs.
• Increases in disease reports were also noted for
  marine mammals.
                              [Ward and Lafferty (2004)]
         Emergence of novel diseases
The emergence of novel diseases occurs in both
the terrestrial and the marine environment.

These diseases are facilitated by:
     - a new combination of hosts and pathogens
     - creating an environment favoring
     pathogens & stressing hosts

Managing diseases in the marine environment is a
lot more difficult than on land however
           Managing marine diseases

Methods for managing disease on land are not
easily applicable in marine ecosystems:
       quarantine or restricting transportation

•Many species may be wide ranging and their
movements difficult to predict/uncontrolable
•Marine species produce copious amounts of
eggs/larvae which are adapted for long distance
dispersal – aids widespread disease transfer
•Many marine species are colonial – lack of genetic
diversity                     [McCallum et al. (2004)]
       Rapid spread of marine diseases

Researchers analysed the rate of spread of marine
diseases – extremely rapid:
   • herpes virus spread through pilchard
   populations a a rate greater than 10,000km
   • morbillivirus spread through whale and
   dolphin populations at a rate of 3,000km year-1

In comparison, only myxomatosis in rabbits and
West Nile Virus in birds, have spread at a rate of
greater than 1000km year-1
          Conditions favoring outbreaks
What causes increased stress on marine organisms?
     - Changes in environmental conditions
          - Climate Change
                 - thermal stress in corals
                 - increased pathogen growth
                 - range changes in pathoges & host
                 = exposure to new hosts or pathogens.
     Conditions favoring outbreaks
- Changes in environmental conditions
     - Anthropogenic causes
            - Nutrient loading
                   - increased bacteria growth
                   - decrease light (UV)
            - Partially/untreated sewage outfalls
            - Chemical pollutants (immune suppressors)
            - Wildlife trade
            - Aquaculture
                   - non native species
                   - anti-biotics
Black band disease on coral in the Caribbean
          Case study: Coral disease
• Black band disease (BBD) is believed to be caused
  by Phormidium corallyticum

• Healthy corals may get BBD through contact with
  an infected coral but diseased corals do not always
  occur in the same site -can be separated by great

• BBD can be spread by currents?

• Corals under stress are more likely to be infected
  and BBD has a higher rate of infection in warmer
          Case study: Coral disease

• Seasonal temperatures changes may affect the
  spread of BBD

• Anthropogenic warming of ocean water
  temperatures may also increase BBD.

• BBD was also found to be more abundant near
  anthropogenic disturbances.
The fungus Aspergillosis on a sea fan
        Case study: Coral disease

• Experiments were conducted that increased
  nutrient concentrations up to 10 times around
  sea fans infected with Aspergillosis.

• There was an increase in the spread of the
  disease (about twice as much) compared with
  colonies that had no extra nutrients.
        Case study: Coral disease

• A similar nutrient experiment was conducted
  with a hard coral (Montastrea)
• similar results – up to 50% of the coral became
  infected when nutrients were increased.

• The infectious agents that cause the diseases
   probably feed off the nutrients
 - which are normally in short supply in tropical
   waters (oligotrophic).

• So the more nutrient input from storm runoff
  the more stressed the corals become.
               Source of disease pathogens
Salmonella spp., Escherichia coli, Streptococcus sp.,
Staphylococcus aureus, Pseudomonas aeryginosa, Candida fungus
enterovirus, hepatitis, poliomyelitis, influenza, and herpes.

      - Animal feces
      - Fungal spores – either air-borne or in storm runoff

Animal transport…
   Marine transportation of livestock
• Every year 6 million sheep and 1 million cattle
  are transported by sea.

• The waste of these 7 million terrestrial animals is
  directly into open ocean.

  In addition…
• 2002 – an estimated 14,500 animals were
  reported to have died at sea and were thrown

• But the actual numbers may be closer to 9% of
  all transported animals = 630,000
    Common terrestrial diseases found in
           marine ecosystems
 Measles – Marine mammals
 Canine distemper – Marine mammals
 Toxoplasmosis – Marine mammal - sea otters
 Herpes virus – Sea Turtles
 San Joaquin Valley Fever – Marine mammals – sea otters
 Aspergillosis fungus- Corals
 Brucellosis – Marine mammals - cetaceans
Green turtle with fibropappiloma tumors
on it. These have been associated with
the herpes virus.
Case study: Toxoplasmosis in dolphins

• 98% of 141 Atlantic bottlenose dolphins
  immunologically tested positive for the
  pathogen Toxoplasma gondii
  -the pathogen causes marine mammal
  mortality via encephalitis (toxoplasmosis).

• The source of this pathogen is likely to be cat
  excrement flushed out into the marine
  environment in sewage or via runoff.
Case study: Toxoplasmosis in dolphins

• Also, 91% of 47 dolphins tested positive for
  Neospora caninum - a causes agent of
  encephalitis in livestock.

• The only known host for this pathogen are dogs
  – pet or stray dog excrement entering the
  marine environment via sewage or surface
  runoff is probably the source of the pathogen

• Exposure to pathogens in dolphins may be
  substantial, which are indirectly anthropogenic
  in source.
Case study: Toxoplasmosis in dolphins

• Also, 91% of 47 dolphins tested positive for
  Neospora caninum - a causes agent of
  encephalitis in livestock.

• The only known host for this pathogen are dogs
  – pet or stray dog excrement entering the
  marine environment via sewage or surface
  runoff is probably the source of the pathogen

• Exposure to pathogens in dolphins may be
  substantial, which are indirectly anthropogenic
  in source.
     Case study: Brucella in whales
• Japanese researchers described testicular
  lesions in 33% of sampled male North Pacific
  minke whales – taken in their scientific
  whaling program [Ohishi et al. (2003)]
• Blood serum tests were antibody positive in
  38% of minke whales of both sexes for the
  pathogen Brucella spp. [Ohishi et al. (2003)]

• Brucella spp. cause brucellosis in mammals.
• Symptoms = joint and muscle pain, and
  epididymitis and inflammation of the testis in
  males and the induction of abortion in females.
    Case study: Brucella in whales
• The high rate of pathogen infection has
  implications for minke whale health and
  reproductive rate/recovery from
• But Brucella spp. has also been
  documented as being capable of causing
  infections in humans.
• The high prevalence of Brucella in North
  Pacific minke whales has implications for
  human health
  – those working with infected carcasses
  – those consuming contaminated products
             Another worry…
• A study on antibiotics in sewage waters
  determined that three antibiotics could be detected
  up to 500 m from the discharge site.
• Also bacteria in the treatment plant were resistant
  to all the antibiotics (n=6) researchers tested on the
• Bacteria collected from discharge waters displayed
  resistance to two of the antibiotics tested.
• The increasing prevalence of antibiotics and
  antibiotic-resistant pathogens in the aquatic
  environment “pose a potential threat to ecosystem
  functions and…human health”.
                                 [Costanzo et al. (2005)]
       Marine disease research needs

 Develop rapid response capability to identify, study, and manage
disease outbreaks as they occur.
 Document longevity and host range of infectious stages.
 Better understanding of environmental facilitators of disease and
host immunity.
 Develop molecular and microbiological diagnostics that can
identify and track pathogens - to trace origins and their spread.
Develop forecasting models for outbreaks with environmental or
climate sensitivity.
 Determine better management of land-based sources of
Costanzo, S.D., Murby, J. and Bates, J. 2005 Ecosystem response to antibiotics entering the aquatic environment.
      Marine Pollution Bulletin 51: 218-223

Dubey, J.P., Zarnke, R., Thomas, N.J., Wong, S.K., Van Bonn, W., Briggs, M., Davis, J.W., Ewing, R., Mense, M.,
     Kwok, O.C.H., Romand, S. and Thulliez, P. 2003. Toxoplasma gondii, Neospora canium, Sarcocystis neurona,
     and Sarcocystis canis-like infections in marine mammals. Veterinary Parasitology 116: 275-296.

Grillo, V., Parcons, E.C.M., Shrimpton, J.H. 2004. A review of sewage pollution in Scotland and its potential impacts
       on harbour porpoise populations. Paper presented to the Scientific Committee at the 53nd Meeting of the
       International Whaling Commission, 3-16 July 2001, London. SC53/E13.

Harvell, C.D., Kim, K., Burkholder, J.M., Colwell, R.R., Epstein, P.R., Grimes, D.J., Hofmann, E.E., Lipp, E.K.,
     Osterhaus, A.D.M.E., Overstreet, R.M., Porter, J.W., Smith, G.W., Vasta, G.R. 1999. Emerging marine diseases
     – climate links and anthropogenic factors. Science 285: 1505-1510.

Kim, K. et al. 2002. Disease and Conservation. Diseases and Conservation Biology working group of the National
     Center for Ecological Analysis and Synthesis.

McCallum, H., Harvell, D. and Dobson, A. 2003. Rates of spread of marine pathogens. Ecology Letters 6:1062-1067.

McCallum, H.I., Kuris, A., Harvell, C.D., Lafferty, K.D., Smith, G.W. and Porter, J. 2004. Does terrestrial
      epidemiology apply to marine systems? Trends in Ecology and Evolution 19: 585-591

Ohishi, K., Zenitani, R., Bando, T., Goto, Y., Uchida, K., Maruyama, T., Yamamoto, S., Miyazaki, N. and Fujise, Y.
      2003. Pathological and serological evidence of Brucella-infection in baleen whales (Mysticeti) in the western
      North Pacific. Compartative Immunology and Microbiolology of Infectious Diseases 26:125-136

Ward, J.R., Lafferty, K.D. 2004. The elusive baseline of marine disease: Are diseases in ocean ecosystems increasing?
      PLOS Biology 2: 542-547.

To top