Ch. 8 PP Notes

Ch. 8 PP Notes - Introduction Wildlife Diseases Heather...

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1 Wildlife Diseases Heather Whitlaw Texas Parks and Wildlife Department Introduction Wildlife diseases originate from infectious and non-infectious pathogens such as viruses, bacteria, parasites, and toxic materials that impair the normal body structure and/or function of individuals , and potentially affect the dynamics of host populations . Individuals At the individual level, diseases can be considered as something “out of the ordinary” Populations Diseases can affect the dynamics of wildlife populations through factors such as mortality and reproductive rates, and vulnerability to other causes of mortality. Also can affect conservation of threatened and endangered species, and reduce potential yield of harvested populations Definitions ± Life cycle, definitive host, intermediate host, transmission, vector, reservoir ± Pathogen, parasite, ectoparasite, endoparasite ± Enzootic, epizootic, zoonosis Disease: the effect of a parasite or pathogen upon the host Most parasites and pathogens have little effect on their hosts. However, signs of disease may be more pronounced when… a) The infection is trans-species b) Infective stages are in the wrong host c) The host is in a reduced state of health Death of the host is unusual and occurs only if… a) Serious illness facilitates transmission b) The parasite does not depend on the infected host for survival and can complete its life cycle after the host dies
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2 How are diseases spread? ± EPIZOOTIOLOGY concerns the ecology of diseases, asking the questions “how” and “why” ± Diseases are ENZOOTIC in the chronic form and EPIZOOTIC when they erupt What is a LIFE CYCLE? ± Definitive host: home for the adult reproductive stages of the parasite ± Intermediate host(s): home(s) for a all other life stages of the parasite (juvenile and infective stages) ± In order for a disease to maintain itself in a host population, it must spread. Therefore, the parasites’ life cycle (TRANSMISSION CYCLE) must be completed ± Assuming that these cycles are complete, factors such as host density, reproductive rate of parasite, transmission rates, and disease- caused mortality rates affect how the disease will spread Parelaphostrongylus tenuis life cycle Why do we study wildlife diseases? ± Wild and/or domestic animals may serve as RESERVOIRS or VECTORS for parasites and pathogens that ultimately affect each other, individuals of other animal species (domestic or wild), and/or humans For example: Brucellosis in Yellowstone National Park, Montana Why do we study wildlife diseases? (continued) ± We need to understand the relationships between wildlife diseases and animal population numbers ± Diseases may cause serious losses in already small populations of threatened or endangered species ± Diseases are a part of the whole spectrum of issues facing wildlife managers
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3 Parasitism vs. Predation ± Both predation and parasitism can reduce the average standing crop of the prey or host species PREDATION places potential prey into 1 of 2
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This note was uploaded on 11/14/2010 for the course AGSC 2301 taught by Professor Middleton during the Spring '09 term at Texas Tech.

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Ch. 8 PP Notes - Introduction Wildlife Diseases Heather...

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