Avian malaria in the African black-footed penguin in the Zoo Basel.
Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute,, an associate institute of the University of Basel (Leitung: Prof Christian Lengeler).
Background: Avian malaria is causing high mortality rates in arctic birds in general, and in penguins in zoological gardens around the world. To reduce the malaria infection rates of the African black-footed penguins (Spheniscus demersus) in the Zoo Basel, mosquitoprevention strategies are required. In order to achieve this, mosquito infection rates and abundance must be monitored in proximity of the penguin enclosure. In addition, endemic birds should be surveyed for their parasite load. This will allow defining the parasite reservoir, as well as the most relevant transmission parameters.
Aim: The aim of this MSc thesis is to study and describe the epidemiology of avian malaria in S. demersus in the Zoo Basel.
Methods: Adult mosquitoes were collected monthly from May to September 2011 in and around the Zoo Basel. The mosquito species were identified and a sub-sample was used to determine the infection status using nested PCR. Mosquito larvae were sampled from all water bodies in and around the zoo during the same time period. In addition, blood samples from 23 African black-footed penguins were collected at the time of peak transmission (1st September 2011) to determine the prevalence rate of Plasmodium spp. in the zoo’s colony. Blood samples from other zoo birds as well as wild birds examined by the zoo veterinarians due to routine health check-up, disease or injury were also investigated for Plasmodium spp. from March to November 2011.
Results: 14,124 adult mosquitoes belonging to eight different species were captured. More than 99 % belonged to the species complex Culex pipiens/torrentium. In three subsamples of 96 gravid female mosquitoes the numbers found positive for Plasmodium infections were 7.3 % (July), 4.2 % (August) and 5.2 % (September). In total, 62 water bodies could be identified inside the zoo and 49 of them were sampled for mosquito larvae at least once. 34 to 42 sites were sampled per month. Out of them 16 to 19 were found positive for mosquito larvae. Around the zoo, only three mosquito breeding sites could be detected. Two African black-footed penguins and one snowy owl were identified with a Plasmodium relictum infection.
Discussion/Conclusions: Although the infection rates in mosquitoes were high and female mosquitoes were present in great numbers, prevalence of avian malaria in the birds was low. To reduce the mosquito population, breeding sites inside the zoo should be controlled. The low prevalence of parasitaemia in the African black-footed penguin population is likely to be due to the fact that the stringent prophylaxis protocol is working. The time frame for prophylaxis could be shortened, only if the mosquitoes show no infection in spring.