Kayoko Matsuo

Potential remedy against Echinococcus multilocularis in wild red foxes using baits with anthelmintic distributed around fox breeding dens in Hokkaido, Japan

The effect of bait-delivered anthelmintic to reduce the prevalence of Echinococcus multilocularis in wild red foxes was evaluated in Koshimizu, in the eastern part of Hokkaido, Japan. The study area (200 km2) was divided into baited and non-baited sections. The anthelmintic baits were distributed around fox den sites in the baited section every month for 13 months. After 1 year of the anthelmintic bait distribution, the prevalence of E. multilocularis in foxes, evaluated either by the parasite egg examination (from 27.1 to 5.6%) or coproantigen ELISA (from 59.6 to 29.7%), decreased in the baited section contrasting to that in the non-baited section (parasite egg: from 18.8 to 24.2%; ELISA: from 41.9 to 45.8%). The prevalence of E. multilocularis in grey red-backed vole Clethrionomys rufocanus, caught around fox dens, born after bait distribution also decreased and was significantly lower than that in non-baited section. However, within the study periods, the coproantigen-positive rate in fox faeces sporadically increased, while egg-positive rate constantly decreased. Since coproantigen ELISA can detect pre-patent infection, this observation indicates that reinfection pressure in the baited section was still high even after the 13 months of anthelmintic bait distribution. Therefore, the bait distribution longer than our study period is required for the efficient control of E. multilocularis in wild red fox population.

Seroprevalence of Toxoplasma gondii infection in cattle, horses, pigs and chickens in Japan

The presence of antibodies to Toxoplasma gondii in livestock and poultry was investigated by latex agglutination tests; samples that agglutinated at dilutions of 1:64 or higher were regarded as positive. Sera were collected from fattening beef cattle (102 Japanese black, 105 crossbreeds and 114 castrated Holstein), culled dairy cattle (101 Holstein), 100 horses, 115 fattening pigs and 235 chickens (163 free-range and 72 broilers) at abattoirs in Gifu Prefecture, Japan, from August 2012 to August 2013. Antibodies to T. gondii were found in 7.3% (31/422) in cattle, 5.2% (8/155) in pigs, but not in horses or chickens. These results suggest that toxoplasmosis may be transmitted to humans via consumption of T. gondii-infected raw beef in Japan.

First report of Trichinella nativa in red foxes (Vulpes vulpes schrencki) from Otaru City, Hokkaido, Japan

Forty-three red foxes (Vulpes vulpes schrencki) and nine raccoon dogs (Nyctereutes procyonoides viverrinus) were captured in Otaru City, Hokkaido, Japan and examined by muscle digestion for the presence of Trichinella sp. larvae. Of the foxes, five (11.6%) were positive for larvae of Trichinella nativa while none of the raccoon dogs were found to be positive. This finding suggests that the red foxes are important reservoir hosts of sylvatic trichinellosis in Otaru, Hokkaido. This is the first report on Trichinella nativa in wild red foxes of Hokkaido, Japan.

Development and sexual maturation of Echinococcus vogeli in an alternative definitive host, Mongolian gerbil (Meriones unguiculatus).

An alternative definitive host model for Echinococcus vogeli was developed using Mongolian gerbils. The animals treated with prednisolone tert-butylacetate were orally inoculated with protoscoleces of E. vogeli and the development of worms in the small intestine was observed until 50 days post infection (DPI). The parasites were recovered most frequently from the anterior part of the small intestine. The band formation (the sign of proglottisation) of the worm was observed at 7 DPI, the second proglottid and tests formation at 14 DPI, spermatozoa in seminal receptacle and cleavage of ova in uterus at 21 DPI, the hook formation of oncospheres at 28 DPI and the embryophore formation at 34 DPI. Eggs in the feces were first detected at 35 DPI. The coproantigen detection method developed for E. multilocularis could detect the E. vogeli coproantigen early in the infection, at 7 DPI during the prepatent period. Therefore, this technique could be used for the diagnosis of E. vogeli, replacing ordinary fecal egg examination.

Venison, another source of Paragonimus westermani infection

Paragonimiasis is a typical food-borne parasitic disease, endemic in most parts of Asia, with sporadic case reports from American and African countries. The major source of infection is undercooked freshwater crab or crayfish, though consumption of wild boar meat is also responsible for the infection in Japan, because wild boar is a paratenic host for Paragonimus westermani. Recently, living juveniles of P. westermani were isolated from muscle of a sika deer, Cervus nippon, in Japan, raising the possibility that venison has been another source of infection. In order to clarify the potential contribution of venison consumption to the occurrence of paragonimiasis, we analysed dietary histories of those paragonimiasis patients in whose diagnoses we were involved between 2001 and 2015. Among 380 patients, freshwater crab had been consumed by 208 patients, wild boar meat by 190, and wild deer meat by 76 patients before the onset of the disease. Overall contribution of wild deer meat was estimated to be 6.8% to 20.0%, although in Oita and Gifu Prefectures, where a substantial proportion of patients had consumed raw venison, the contribution of venison consumption was much higher (27.5 to 62.1% and 42.1 to 78.9% in Oita and Gifu Prefectures, respectively). We demonstrated P. westermani-specific antibodies in the sera of 4 out of 160 sika deer from Gifu Prefecture, strongly suggesting that these deer were infected with P. westermani.

Dose dependency of prednisolone tertiary-butylacetate (PTBA) treatment on the establishment and site predilection of Echinococcus multilocularis in an alternative definitive host model using Mongolian gerbil (Meriones unguiculatus)

Abstract Mongolian gerbils (Meriones unguiculatus) were orally inoculated with 10,000 protoscoleces of Echinococcus multilocularis per head after being divided into five groups (A–E). Each group was dosed with prednisolone tertiary-butylacetate (PTBA) as follows: A, 0 mg; B, 0.5 mg; C, 2 mg; D, 5 mg; and E, 10 mg/head. All animals were injected subcutaneously with control solvent or PTBA every other day from 6 days pre- to 6 days post-infection. Autopsy was performed at 7 days post-infection. Doses of PTBA and the number of worms recovered showed a positive correlation (r=0.929, P < 0.0001). In groups A, B and C, the predilection site of the worms in the small intestine could not be determined, while in group D the worms were found more in the anterior part. In group E, the predilection site was the anterior part, followed by the middle and the posterior parts of the small intestine (Fishers test: P < 0.01). The number of worms recovered from the anterior and the middle part of the small intestine also correlated positively with PTBA dose (anterior part: r=0.930, P < 0.0001, middle part: r=0.917, P < 0.0001). All groups of the PTBA-treated animals showed significant loss of weight compared to the non-treated animals (P < 0.01).