Lecture 13 FNR 251
Popular in Ecology And Systematics Of Amphibians, Reptiles, And Birds
Popular in Agriculture and Forestry
This 29 page Class Notes was uploaded by Sierra on Monday February 29, 2016. The Class Notes belongs to FNR 251 at Purdue University taught by Rod N. Williams in Spring 2016. Since its upload, it has received 9 views. For similar materials see Ecology And Systematics Of Amphibians, Reptiles, And Birds in Agriculture and Forestry at Purdue University.
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Date Created: 02/29/16
Amphibian & Reptile Diseases Emerging Infectious diseases • Pathogens may be newly introduced to an area where populations have no previous exposure or immune response – Zoonose = infectious disease that can be transmitted between species (usually wild animals & humans) – Introduced species: vectors/reservoirs for disease organisms Categories of Infectious agents • Pathogens: –Bacterial –Fungal –Viral –Parasitic (Metazoan, trematode)s Bacterial: Salmonella • Many reptiles & amphibians are likely carriers or susceptible – Reptiles more prevalent – Most significant zoonotic pathogen of reptiles • Handling or ingestion • Higher carrier rate in captive reptiles Bacterial: Salmonella • Pet turtles • Up to 90% reptiles carry strains in GI tract – Bacteria shed in feces • Salmonellosis = bacterial infection in humans • More serious in children Water Mold • Saprolegnia sp. • Widespread, common worldwide • Oomycete (egg fungi) = Secondary superficial infections in fish and amphibians • Greatest impact on egg masses – Significant mortality – Appears as “white fuzz” under microscope Water Mold • Saprolegniasis: potentially lethal infection with fungus • Some herps: – Bufonids – Ranids – Hylids – Ambystomids – Cryptobranchids Chytrid • Chytrid, Batrachochytrium dendrobatidis, “Bd” • Fungus attacks keratinized tissue – in skin of adults – Mouthparts of tadpoles (oral disc) • Chytridiomycosis: fatal disease caused by the fungus • Appears to have low host specificity – Chytrid fungus: 94 of 120 species of frog species extinct since 1980 Chytridiomycosis • Skin becomes thick (hyperplasia, hyperkeratosis) • Interferes with absorption/osmoregulation of water, oxygen, sodium & potassium, electrolytes • Individuals suffocate, or abnormal electrolyte levels – can cause heart to stop beating Life Cycle Chytrid Distribution The Ecology of Chytrid • Lips 2006: Bd can likely spread in mist/clouds • Persist for several months • Not restricted to local water contact • 100 km/yr Bd • Captive treatment: – Itraconazole bath – Elevate body temperature • Wild: Some individuals remain, “persist” in populations following some mass mortality events • Persistent populations could bounce back over time • Wild?... Treat small percentage of individuals: reduce intensity of infection, Symbiotic Bacteria, & Peptide secretion treatment Chytrid • Can persist on mud on boots, nets • Disinfect Low 1-3 % bleach solution • Dry for 3 hrs kills chytrid • Use gloves when sampling individuals Malformations • Increasing number of reports of malformed frogs in other locations – 44 states representing 60 species • Are malformations a significant factor contributing to population declines? Examples of malformations • Polymelia • Polyphalangy • Brachydactyly http://www.nwhc.usgs.gov/rese arch/amph_dc/frog.pdf Purported Causes of Malformations • Chemical contamination • Exposure to UV light • Parasites? – Ribeiroia sp. Malformation in Salamanders Adult Malformations Ectrodactyly Polyphalangy Brachydactyly Polymelia Larval Malformations Larval Malformations Larval Malformations Ranaviruses • Family: Iridoviridae • Ranavirus sp. (6 species) • Double stranded DNA virus • Every Continent • More Recent “Emerging” disease Ranavirus • Dieoffs: – 25 states – 20 amphibian species – 2 chelonian species Ranavirus • Viral infections common at high densities • Mortality highest in larvae approaching metamorphosis • Ranavirus can eliminate local populations Ranavirus • Disease transmission – Direct contact – Necrophagy – Indirectly via water & fomites – Other vectors? • Sublethal effects: some individual metamorphs may carry to other ponds? Ranavirus • Human assisted transport – Salamander bait (Collins et )l. 2003 • Stocking ponds & lakes Ranavirus: Molecular Genetics • Multiple strains – Anurans & Urodeles • FV-3 (frog virus 3) highly virulent ranavirus • No cure….
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