Unusual Prevalence of Avian Malaria (Plasmodium sp.) in the Adult Population of Humboldt Penguins (Spheniscus humboldti) at an Israeli Zoo Between Years 2012 and 2015.

Avian Malaria is a vector borne disease caused by protozoan blood parasites of the genus Plasmodium, transmitted exclusively by mosquitoes (Culicidae) to a variety of birds. However, a few avian groups, including penguins (Sphenisciformes), are considered highly susceptible and may develop severe disease when exposed to these parasites. Clinical signs vary from asymptomatic presentation to per-acute mortality, depending on the susceptibility of the host species. Outbreaks in captive populations of penguins have often led to high morbidity and mortality rates. We describe an unusual prevalence of Avian Malaria caused by Plasmodium spp. in the adult population of Humboldt penguins (Spheniscus humboldti) at an Israeli zoo between years 2012 and 2015. The laboratory diagnostic methods included screening for Plasmodium by blood or touch smears stained by Giemsa, nested polymerase chain reaction (PCR) and histopathology. During this period, 14 penguins were found dead while 8 of them (3 females, 5 males) were definitively diagnosed as malariapositive. Some penguins were found dead without previous detected clinical signs, however, some of them presented with non-specific clinical signs such as weakness and anorexia. Most of the mortalities occurred in the summer months between June and August. The age range of those 8 malaria-positive penguins at death was between 2-12 years, with a mean and standard deviation of the mean of 7.2 ± 3.4 years. As malaria is considered usually a disease of young penguins up to three years of age, the unusual advanced age of infection, uncommon in zoos in Israel previously, is worth noting and should require the continuing monitoring for malaria as a significant cause of penguin mortality in Israeli's zoos. [ABSTRACT FROM AUTHOR]