PaBi (17): immunoepidemiology of macroparasites Flashcards
Give examples of some macroparasites.
Fleas, ticks, lice, helminths
What is epidemiology?
The study of the incidence and distribution of a disease and how it can be controlled.
What are some features of macroparasites?
large multicellular organisms- visible to the eye, antigenically complex, don’t multiply in the host- increase in parasites within the host caused by reinfection, complex life cycle, long generation times.
Briefly, what is the Ro of macroparasite?
The number of offspring produced and reaching maturity in an ideal world i.e. no competition, no immune response.
What is the exact Ro definition?
The average number of female offspring produced throughout the lifetime of a mature female parasite which themselves achieve reproductive maturity, in the absence of density-dependent constraints on the parasite establishment, survival or reproduction.
How are levels of macroparasites measured?
Either directly by counting the number on the skin or indirectly for endoparasites by taking faeces/ urine samples, passing them through a filter so the eggs stick and counting the eggs under the microscope.
What are the epidemiological patterns of ticks?
Tend to affect older cows more and in December
What is the benefit of knowing the epidemiological patterns and seasonal variations of a parasite?
Allows you to know when is best to treat and which animals are best to treat if you have little money and can’t treat them all.
What is the statistic for the frequency distribution of schistosomiasis?
The 20-80 rule- 20% of the people have 80% of the infection so it’s best to try and treat that 20%
Why is it beneficial to look for the age group that is most infected?
Allows identification and easier treatment of the people who carry most of the infection.
What is peak shift?
This is a relationship between age and peak levels of infection- at high transmission rates, peak infection will be at a younger age compared to lower transmission rates.
Who is most predisposed to re-infection after treatment?
The same group that had the highest incidence of infection the first time because they still have the highest exposure e.g. they still drink/ wash with the same infected water.
How can you assess peoples exposure to an infective agent?
Identify exposure sites and people’s behaviour e.g. who uses the contaminated sites and what for- boys/girls, men/women, swimming/washing/drinking. Look at exposure history by using questionnaires or taking blood samples to test for antibodies.
In lambs, what factor accounts for 30% of their susceptibility to helminths?
Genetic factors- can breed for certain resistant genotypes.
What are the benefits of herd immunity?
When large numbers of the population are immune, it is harder to carry on the chain of transmission in diseases passed from person to person.
