ABSTRACT. Group A consisted of chickens infected with a single dose of Ascaris suum and group B of chickens infected with two successive doses. At days 1, 3, 7, 14 and 21 after the first or second infection dose, six chickens from each group were sacrificed. In both groups, larvae were recovered from the livers on days 1, 3, and 7 and lungs on days 3 and 7. No larvae were detected in chickens on day 14. Clear white lesions were noticed only on the livers from chickens of group B at day 7 but had disappeared at day 14. A comparison with group B showed mild histological changes that developed relative to the livers from group A. KEY WORDS: Ascaris suum, chickens, visceral larval migrans.J. Vet. Med. Sci. 70(10): 1129-1131, 2008 Similar to the visceral larval migrans (VLM) of Toxocara canis (T. canis) infection [3], Ascaris suum (A. suum) infection in humans has been reported in Japan [2,8,10,11,15]. It was considered that at least three human cases were caused by eating fresh raw meat and liver from cattle or chickens [2,8,10]. These reports suggest that chickens may play an important role in the zoonotic transmission of A. suum. To clarify the VLM of A. suum larvae in infected chickens, an investigation was carried out on the distribution of larvae and the pathological changes in the livers.Fresh A. suum eggs were obtained from female worms at a local abattoir. Embryonation of the eggs was performed as described by Tsuji et al. [16]. A total number of 65 male broiler chickens aged about 20-days old were used. Initially, groups A (chickens infected with a single dose of A. suum) and B (chicken infected two successive dose) of 30 chickens each received 10,000 eggs and were kept in cages. The same number of eggs were given again to chickens of group B 17 days after the first dose. On days 1, 3, 7, 14, and 21 after the first or second infection, six chickens from each group were sacrificed by cervical dislocation. Larvae were collected from the liver (lobus dexter), lung, pectoral muscle (musculus pectoralis profurdus; about 30 g), and the duodenum (without contents and mucus) using the Baerman method. The contents and mucus of the duodenum were fixed separately in 5% formalin solution and examined microscopically. A video micrometer was used for the measurement of the length of larvae. Statisitical analysis of differences in larval counts between both groups on the same day after first or second infection was done using Statisitica (Stat Soft, Tulsa, OK, U.S.A., P<0.05). The liver (lobus sinister) was investigated macroscopically and fixed in 10% buffered formalin solution. Paraffin sections were stained with hematoxylin and eosin (HE) or with Azan. To examine the lesion in repeatedly infected animals, remaining 5 chickens (group C) were infected with 10,000 eggs twice weekly for five weeks and sacrificed 7 days after the final infection.No clinical signs were observed in any of the infected chickens during the study period. Table 1 shows the distribution of A. suum larvae in chickens of groups A and B. Larvae were ...