In the present study, we investigated the effect of systematic tick control programs for reducing Theileria orientalis (TO) infection in heifers and ticks. Grazing heifers in two selected public pastures in Kushiro, Hokkaido, which had been previously known for a high prevalence of TO, were treated with acaricides for a period of three years starting from 2011. Blood samples collected from heifers and ticks collected from grasses were analyzed as follows: morphological identification of ticks, TO infection in heifers and ticks, and anemia status in cattle. Several heifers in both pastures were PCR-positive for TO before the beginning of grazing, and only the TO-negative heifers were subsequently monitored to evaluate the impact of the tick control programs. Three tick species, including Ixodes persulcatus, I. ovatus and Haemaphysalis douglasi, were found to be active in both pastures during spring, and TO was detected by PCR in all three tick species. During the study period, a gradual decrease was observed in the parasite burden among the ticks and in the numbers of animals that developed TO infection. Additionally, a gradual reduction in anemia rates was also observed among these animals as the tick control programs progressed. These findings suggest that the implementation of systematic tick control strategies for several years, together with the continuous monitoring of TO infection in heifers and ticks, is effective in reducing the prevalence of this parasite among heifers in these pastures.
Lawsonia intracellularis infections primarily occur in foals after weaning. The infection has recently been identified in Japan, but many clinical and etiological questions remain regarding the disease. In December 2012, symptoms such as fever, decreased appetite, edema, leukocytosis, and diarrhea were observed in four of eight foals on a thoroughbred breeding farm in Hidaka, Hokkaido. Tetracyclines were administered and all foals recovered. L. intracellularis genes were detected with polymerase chain reactions in feces from one of four asymptomatic foals, as well as from two of the four symptomatic foals. Asymptomatic foals were thus suspected to have subclinical infections.Because antibodies against L. intracellularis were detected in all foals using indirect immunofluorescence assay, all foals were considered to have been infected with L. intracellularis. Although the total serum protein (TP) levels were lower in symptomatic foals than in asymptomatic foals, TP levels in asymptomatic foals were still significantly lower than those of foals from the same farm measured in the preceding two years.
From July 2012 to December 2012 (for six months), hepatic grayish white solid nodules were observed in 53 of 610 horses brought to a slaughterhouse in Fukuoka Prefecture. We performed both histopathological and genetic examinations on these materials to investigate larval Echinococcus multilocularis infections. Based on the results of these examinations, 39 horses were diagnosed with alveolar hydatid disease (the infection rate was 6.4%). Infections of larval E. multilocularis were observed not only in light breed horses, as has been reported previously, but also in various other types of horses, including ponies, Japanese draft horses and Hokkaido ponies. In the epidemiological survey, we were able to confirm that 4 horses had been raised in Hokkaido, where alveolar hydatid disease is endemic, and they might have been infected by larval E. multilocularis there. On the other hand, we could not confirm that most of the horses infected by larval E. multilocularis in the present survey had been raised in Hokkaido, and we had difficulty in detecting where they had been infected by larval E. multilocularis. But, considering the regional distribution of E. multilocularis in Japan and the statistical analysis data of horses born in Japan, we could not completely deny the possibility that they also might have been infected by larval E. multilocularis in Hokkaido.