Epidemiology, histpathology, and muscle distribution of Trichinella T9 in feral raccoons (Procyon lotor) and wildlife of Japan

The prevalences of Trichinella T9 in trapped raccoons (Procyon lotor) and several other potential mammalian reservoirs in Hokkaido, Wakayama, and Nagasaki Prefectures were investigated. Muscle samples were collected from 2003 to 2006 from 1,080 raccoons, 113 raccoon dogs including 2 species (Nyctereutes procyonoides albus and N. p. viverrinus), 41 wild boars (Sus scrofa leucomystax), 14 martens (Martes melampus), 10 badgers (Meles meles), 5 Siberian weasels (Martes sibirica coreana), 7 mink (Mustela vison), and 1 red fox (Vulpes vulpes japonica). The samples were digested, and the prevalence and mean intensity of infection with the Trichinella muscle larvae were determined. The prevalence and intensity of the muscle larvae were 0.9% and 93.3 larvae/g (range 0.4-201.8) in raccoons, and 1.6% and 61.6 larvae/g in raccoon dogs, respectively. The infected animals were captured in different areas in Hokkaido Prefecture. These results confirmed that raccoons, which have been introduced from North America since the 1970s, are involved in the sylvatic cycle of Trichinella in Japan. In raccoons, the muscle density of Trichinella T9 larvae was highest in the tongue, and larvae were not found in the heart muscle or diaphragm. This is the first report of Trichinella T9 infection of feral raccoons in Japan.