Epidemiology of fishborne trematodiasis in Kazakhstan

Fish borne trematodes are an important cause of morbidity in Kazakhstan. The number of human cases of opisthorchiidosis (infection with parasites of the family opisthorchiidae) reached a peak of 2521 recorded cases (17 cases per 100,000) in 2002 with a gradual decline to 1225 cases (7.4 cases per 100,000) in 2011. Most human cases are found in the north and north east part of Kazakhstan in areas drained by the Irtysh River and it tributaries. A further focus is found in the north west in the Ural river basin in the European part of Kazakhstan. The most common occupations of patients with opisthorchiidosis included the manual laborers, those employed in the home or unemployed. Necropsy investigations of village dogs in an endemic region revealed 37 of 51 (72%) village dogs infected with either Opisthorchis felineus or Methorchis bilis. Likewise an investigation of 242 cats consisting of strays, village, suburban and city cats revealed 79 (33%) animals infected with O. felineus. Higher prevalences were seen in strays and village cats compared to suburban cats. No urban cats, which lived in apartments, were found to be infected. Other important zoonoses included Echinococcus granulosus, detected in 2 of the 51 necropsied village dogs and E. multilocularis was found in 2 out of 124 necropsied stray cats. Investigations of locally caught fish revealed 10 of 107 (9%) roach (Rutilus rutilus), 49 of 68(72%) ide (Leuciscus idus) and 2 of 79 (2.5%) bream (Abramis brama) infested with trematode metacercariae. No metacercariae were found in 609 crucian carp (Carassius carassius), 35 tench (Tinca tinca), 79 carp (Cyprinus carpio), 46 perch (Perca fluviatilis) or 20 zander (Sander lucioperca).