Prevalence of hydatidosis among donkeys in northern Jordan.

One hundred and thirty donkeys (Equus asinus), aged between 5 months and 14 years of age, from the Irbid Governorate in northern Jordan were necropsied between November 1997-May 1999. Of these animals, 16.9% had hydatid cysts in either their lungs and/or livers. No donkeys of 3 years of age or less were infected, where as 33.3% (22 of 66) aged 4 years or greater were infected. Intensity of infection increased with age in a linear fashion. The prevalence also increased with age approaching an asymptotic prevalence of 1 in the oldest animals. This implied there was minimal regulation of the parasite population by intermediate host immunity. The numbers of cysts in the donkeys were increasing at a rate of 0.48 cysts per year from 0.054 infections. The frequency distribution was highly aggregated, consistent with a negative binomial distribution indicating infection of donkeys was not random.