VETERINARY PARASITES - IMPORTANCE REPRODUCTIVE MECHANISMS HIGH PRODUCTION - LOW SURVIVAL e.g. tapeworm eggs, in huge numbers dispersed to open environment, chance ingestion by intermediate host. LOW PRODUCTION - HIGH SURVIVAL e.g. warble fly eggs in small numbers laid on disease host for the parasitic larvae.

VETERINARY PARASITES - IMPORTANCE OVERDISPERSED DISTRIBUTION OF PARASITES eg. ticks on cattle: 50% of the total ticks on the herd are on 15% of the cattle in the herd FREQUENCY OF INFESTATION TICKS PER COW PERCENTAGE OF HERD 80 small number of cows with many ticks most cows have few ticks

VETERINARY PARASITES - IMPORTANCE PRURITIC STRESS eg. scabies, or sarcoptic mange mites in epidermis mite antigen mast cell in dermis nerve in dermis inflammatory mediators

VETERINARY PARASITES - IMPORTANCE BITING STRESS - eg. Stomoxys flies piercing mouthparts nerve endings in dermis numerous flies

VETERINARY PARASITES - IMPORTANCE ACUTE INFLAMMATORY REACTION eg. babesiosis Babesia infected red blood cell release of inflammatory mediators exponential rate of infection of red cells

VETERINARY PARASITES - IMPORTANCE DESTRUCTION OF HOST TISSUES AND ORGANS eg. Coccidiosis in poultry Eimeria protozoa in epithelium of caecum massive reproduction causes cell disruption

VETERINARY PARASITES - IMPORTANCE COMPETITION FOR RESOURCES eg. Parascaris worm burden nutrients to host nutrients to parasites uninfected host gut

fox or dog final host rodent intermediate host for Echinococcus multilocularis zoonotic infection of human with eggs via dog faeces VETERINARY PARASITES - IMPORTANCE ZOONOTIC INFECTIONS eg. hydatid hydatid cyst larval form of tapeworm in develops in rodent or human natural cycle

infected horse single midge - infection uninfected horse develops from gut to saliva virus develops in midge gut then migrates to salivary gland VETERINARY PARASITES - IMPORTANCE TRANSMISSION OF OTHER PATHOGENS eg. African horse sickness by blood feeding Culicoides midges