Dynamics of parasitic helminth infections: Improved control practices through comparative studies in chickens

Project summary

The main objective of this project is to create capacity in Nicaragua to study the dynamics of parasitic infections. Parasitic diseases are common in both man and livestock but current control measures assume to a large extent that all infections should be eliminated. This is clearly not allways possible and for many parasites of veterinary importance it may be wiser to develop a strategy for how to live with the parasite. This requires, however, methods to study the fate of infections over time (whether immunity develops and at which cost from the host and whether present infections limit the establishment of new infections). The present proposal makes use of newly developed molecular tools to address these practical questions. The outputs of the project will be a PhD degree with four peer-reviewed papers and the methods will also be established in Nicaragua at the UNAN-León and MINSA. The activities will involve PhD courses in Denmark, experimental studies in Denmark, establishment of laboratory methods in Nicaragua and field studies in Nicaragua. This will be followed by a stay in Denmark with writing and defence of the thesis. The research results will be communicated to the scientific community as journal articles and conference papers. At the end of the project a course will be organized in Nicaragua on strategies for parasite control.

Outputs

Completion Report - Summary:

This project is on the importance of parasitic infections in smallholder poultry production in Nicaragua supported by experimental studies to determine central aspects of the biology of the common helminth Ascaridia galli.

Luz Adilia Luna’s PhD project combines field studies of parasitic infections in chickens in Nicaragua with detailed population dynamics studies in Denmark. The field studies in Nicaragua have shown very high prevalences of helminth infections in free-range chickens, that the hosts with the higest parasite burdens have impaired growth rates and that acquired immunity is down-regulating the burden of several helminth species. These findings were nicely complemented by the controlled studies in Denmark Using a newly identified genetic marker it was shown that immunity reduced the establishment of incoming infections rather than affecting the already established parasite population.

The project shows that control of parasitic infections will be beneficial, but as the studies showed that it is difficult to point at a specific age groups of chickens in a specific season as the major target group for intervention, treatment options have to be very low-cost to assure a favourable benefit-cost ratio.

The experimental studies showed that infection with Ascaridia galli provoces a relatively mild immunologic response. Previous exposure decreases the establishment rate of new infections, but it does not completely prevent their establishment.