Diseases of reptiles and amphibians 2011

Diseases of reptiles and amphibians 2011 - Infectious...

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1 Infectious diseases of amphibians and reptiles Kat Hadfield MA VetMb MRCVS November 2011 Infectious agents Prions Viruses Bacteria Fungi Protozoa Apicomplexa Metazoa Trematodes etc • ‘New’ infectious agents are found constantly 2 Infectious diseases Why are some pathogens more significant? High pathogenicity Low infectious dose, easy transmission Naïve hosts Movement of hosts/vectors/antigen Mutation Host immunosuppression Pathogenic to Humans (zoonotic) Domestic or farmed species Threatened or endangered populations 3 Amphibians Order Anura Frogs and toads Order Caudata Newts, salamanders, sirens Order Gymnophiona Caecilians 4 Amphibians Order Anura - frogs and toads Four limbs, no tail (except Ascaphus ) Adapted for jumping/crawling External fertilization American bullfrog Leopard frog Woodhouse toad 5 Amphibians Order Caudata (urodeles) - newts, salamanders Limbs and a tail, some regeneration Some adults have external gills and no lungs (neoteny) Most have internal fertilization, oviparous Spotted salamander Siren 6
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2 Amphibian population declines Significant decline in wild populations globally 2006 data (Mendelson) 5,743 described extant species 23% data deficient 32% threatened <1% showing population increases 122 sp became extinct 1980-2004 (Stuart, 2004) 7 Highest levels of threatened amphibians in Latin America Carribbean 80-92% of species are threatened (IUCN, 2008) 8 9 Amphibian population declines Causal hypotheses Habitat destruction/degradation Increased UVB Climate change (local + global) Introduced species or loss of top predators Environmental contaminants Collection Infectious disease Aeromonas Ranaviruses Chytridiomycosis Ribeiroia trematode 10 Aeromonas Gram negative rod-shaped bacteria Signs: mortalities, inflammation Mountain yellow legged frog Boreal/western toads Diagnosis: cytology, histology, culture Opportunistic, ubiquitous Disease usually secondary to env changes or other pathogens E.g., chytrid, ranavirus (Miller 2008) 11 ‘Red leg syndrome’ Does NOT always mean bacterial septicemia Signs: redness, ulceration, eye lesions, edema, inappetance, lethargy, neurologic and respiratory signs, mortalities (organomegaly, necrosis, congestion) i.e., signs of inflammation Differentials Systemic bacteria (e.g., Aeromonas, Pseudomonas, Citrobacter, Chlamydophila, Mycobacterium ) Systemic virus (e.g., ranavirus) Systemic fungi Systemic toxin 12
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3 Ranaviruses In Iridoviridae family Large group of DNA viruses Bohle (BIV) Tiger salamander (ATV) Tadpole edema (TEV) Frog virus (FV3) 13 Ranaviruses High mortalities in stressed populations N America, Europe European common frog in Britain Tiger salamander in W USA Primary cause of 48% of amphibian mortality
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This note was uploaded on 01/09/2012 for the course ANSC 252 taught by Professor Cindydriscoll during the Spring '11 term at Maryland.

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Diseases of reptiles and amphibians 2011 - Infectious...

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