[Relationship between the prevalence of hepatic milk spots in pig and the egg density of Ascaris suum in Kitakyushu Municipal Meat Inspection and Control Center].

The hepatic milk spots of pigs are chronic interstitial hepatitis, and are caused by the migration of pig ascarid worm, Ascaris suum, into the liver. A large number of livers are condemned in meat inspection centers as defective food once they are found to have developed milk spots, and thus the economic loss is great. Eggs of Ascaris suum from 120 caecum feces of slaughtered pigs were detected by the nylon mesh filtration (Makiya) technique and they were related to the condemnation data of the milk spot livers in Kitakyushu Municipal Meat Inspection and Control Center from April 2000 to February 2001. The condemnation rate was continuously more than 50% at some particular pig farms, the average rate being as high as 73% during this period. Liver milk spots and Ascarid infection from some 200 mg of caecum feces sampled with the template of the filtration technique were compared. As a result, a close agreement was observed between the two kinds of positive data, and a significant correlation was expected between the average egg density (EPG) of sampled pigs and the prevalence rate of milk spots of the same groups. These results proved that this filtration technique can be used as an effective inspection method for detecting milk spot liver.

Recent increase of human infections with dog heart worm Dirofilaria immitis in Japan.

The human infection with Dirofilaria immitis, was reported for the first time in 1964 from a subcutaneous case, and in 1968 from a pulmonary case in Japan. Since that time, a total of human D. immitis cases amounted to 120 cases up to the first half of 1995. Among these, only one infection with D. repens was reported from a southern island of Okinawa. The parasitological aspects of these cases are reviewed along with clinical, pathological, immunological and epidemiological features.

Comparative infectivity and survival of first-stage larvae of Angiostrongylus cantonensis and Angiostrongylus malaysiensis.

Angiostrongylus malaysiensis was isolated from wild rats Rattus norvegicus in a seaport area of Kitakyushu City, Kyushu, Japan in 1990. The infectivity and survival capacities of first-stage larvae of A. malaysiensis and Angiostrongylus cantonensis were compared under various conditions. Infectivity of first-stage larvae of the former in Biomphalaria glabrata was much lower than that of the latter. In an exposure at various pHs, and with various proteases and tissue homogenates of B. glabrata, the survival of first-stage larvae of A. malaysiensis was also lower than that of A. cantonensis. This lower survival was compared to that of A. cantonensis in response to desiccation of rat feces and high water temperature. First-stage larvae of A. malaysiensis thus appear to be influenced by conditions in the host's feces, specifically temperature and desiccation, and also show a greater sensitivity to pH and component proteases in the snail body than A. cantonensis.

Genetic variability in isozymes of Angiostrongylus malaysiensis.

The genetic difference between Angiostrongylus malaysiensis and A. cantonensis was assayed by electrophoretic analysis of isozymes. Six enzymes were analyzed using 5% polyacrylamide gel electrophoresis. Seven of 10 loci, namely GPI-1, GPI-2, HK-1, HK-2, MDH-1, MDH-2 and PGM-2, were shown to be polymorphic, but the remaining 3 loci, LDH, ME and PGM-1, were not. Both A. malaysiensis and A. cantonensis were polymorphic at 6 of the loci (p = 0.600) with heterozygosity H of 0.286 and 0.151, respectively. The Nei's genetic distance (D) between A. malaysiensis and A. cantonensis was 0.27470. This value indicates the level of interspecific variation within a genus. Through isozyme analysis, the present study demonstrated that A. malaysiensis of Japan is a valid species, separate from A. cantonensis.

[Distribution pattern of Dirofilaria immitis microfilariae in peripheral blood of a dog and their intake by mosquitoes].

Experiments were made in which Aedes aegypti mosquitoes fed on a dog infected with Dirofilaria immitis, in order to determine the distribution pattern of microfilariae (Mf) in the dog's periphery blood and the number of Mf taken by the mosquitoes. Mosquitoes fed on an anesthetized dog at some 50 shaved skin spots and they were weighed immediately before and after feeding. This enabled us to examine not only the Mf number taken by each mosquito but also the Mf intake density in terms of Mf number per mg of blood. The Mf intake density showed a wide variation at the different parts of the dog's body, and the frequencies of Mf showed uneven distributions which were fitted best by the negative binomial. Significant differences were detected in the Mf intake density at different parts of the skin, but these differences were concluded as a non-consistent result because a similar result was not reproduced in the next experiment. It was presumed that not only the Mf number per mosquito but also the Mf intake density increased as the blood intake by the mosquitoes increased. This increase of both the Mf number per mosquito and the Mf intake density was also supported by another experiment in which mosquitoes were fed at the same skin spots consecutively one after another.

[Pulmonary dirofilariasis found unexpectedly during thymectomy].

A 56-year-old woman in Kitakyushu City was operated on after diagnosis of mediastinal tumor with myasthenia gravis. Besides the thymoma, a small nodule was palpated in the lower lobe of the left lung and biopsied. A segmented worm was found in sections of this granulomatous nodule. A cross section of the degenerated worm (400 X 310 micron) showed a 3-layered tegument and internal cuticular ridges with high lateral chords. The muscle layer consisted of high and polymyarian muscles. Based on these characteristics, this worm was identified as an immature dog heartworm, Dirofilaria immitis. The recent sharp increase of dirofilariasis cases reported in Japan is discussed.

[A case report of nasal infestation by the leech, Dinobdella ferox].

A 55-year-old man in Okagaki Town, Fukuoka Prefecture, pulled a nasal leech from his nostril in July 1987, after suffering from nosebleed, copious running snivels as well as unpleasant foreign body sensation in the nasal cavity. Except for nasal septum deviation, no abnormality in the ears and mouth cavity nor bleeding, ulcerous and erosive changes in the nasal cavity were found. The formalin-fixed specimen of the leech was nearly black with no definite stripes or spots, and measured 3.5 cm in length and 1.2 cm in width. Because of these and the following characteristics, viz. 1) auricles on the posterior segment were absent, 2) five pairs of eyes were present in the anterior segments with the eye pairs 3 and 4 separated by an annulus, and 3) teeth were not observed, this specimen was identified as Dinobdella ferox. This nasal leech is found widely in Southeast Asia. In Japan, some human cases of its infestation have also been reported, mainly from southern Kyushu. The leech seemed to have entered the nasal passage of the present case from a stream at a hot spring in northern Kyushu. Attention should be given to nasal leech infestation especially now that many people in Japan are eager to visit isolated hot spring resorts.

[Three recent cases of ascariasis in northern Kyushu].

Ascariasis is considered to be one of the rare infectious diseases in Japan, but recently it has been slightly increasing. This paper reports three ascariasis cases who seemed to be infected recently in the Kitakyushu area, Japan. Case 1: A 59-year-old woman in Kitakyushu City passed a round worm after continuous abdominal pain. The patient was discharged from the hospital because of no further abnormal intestinal symptoms and findings. Case 2: An 85-year-old woman in Nakama City, who suffered from cerebral infarction, vomited a round worm before hospitalization. Many ascarid eggs were detected after admission, and after treatment with pyrantel pamoate (Combantrin) two round worms were passed and egg detection became negative. Case 3: A 77-year-old man in Saikawa Town vomited 3 round worms after gastrectomy due to early gastric cancer. Many unfertilized eggs were also detected from the stool together with hook worm eggs, but no eggs were found after administration of pyrantel pamoate. Morphological examination was made by a scanning electron microscope on the denticles on the dentigerous lip ridges of the worms to differentiate from possible infection with a pig parasite, Ascaris suum. The three cases were diagnosed as ascariasis due to human Ascaris lumbricoides based on the following evidences that the expelled worms had 1) less pointed tips of the denticles and shallower or wider interdenticle notches, and 2) far more denticles of smaller size along the dentigerous ridges, compared with Ascaris suum. The necessity of differentiating pig- from human-ascarids, when considering human infection with Ascaris suum, is discussed.

[A human case of pulmonary dirofilariasis suspected to be lung cancer].

A 50-year-old man in Kitakyushu City visited a hospital for evaluation of an opacity in a routine chest X-ray film. After examinations by bronchoscopy and chest roentgenography, a clear coin lesion was found in the middle lobe of the right lung and was suspected to be a lung cancer. A right thoracotomy was performed to remove it. The lesion (10.6 X 9.8 mm) was a well-defined ellipsoid granuloma due to a foreign body with a central zone of necrosis surrounded entirely by a fibrous wall. In a cross section of the dissected granuloma two degenerated worm-like structures were revealed. The sections of the worm (216-240 X 296 mu m at the greatest diameter) had at least a 3-layered cuticle and prominent internal longitudinal cuticular ridges but no external cuticular ridges. The lateral chords were as high as the muscle layer which consisted of abundant somatic muscle (more than 30 muscle cells/quadrant). Judging from these morphological characteristics, the pulmonary granulomatosis was diagnosed to be due to an immature dog heartworm, Dirofilaria immitis. This identification was further supported by results from immunological methods. The present case is the 56th human case of dirofilariasis (the 39th as a pulmonary case only) in Japan.

[Fifty-six cases of human dirofilariasis reported in Japan--a complied table].

Since the first reported case of human dirofilariasis in 1964, a total of 56 cases have been recorded from Japan, including 39 pulmonary and 16 extra-pulmonary cases. The difference in case number between pulmonary and extre-pulmonary sites is statistically highly significant (P = 0.001). Distribution of the lesion in pulmonary dirofilariasis is mainly concentrated in the right lung (P less than 0.001). The rapid increase of human dirofilariasis within the last 5 years indicates that this disease is one of the important anthropozoonoses.

Population studies on Oncomelania quadrasi, the snail intermediate host of Schistosoma japonicum, in the Philippines. 5. Quantitative analysis on successful snail control by land reclamation.

For the control of Oncomelania quadrasi, environmental modifications, i.e., clearing of vegetation, leveling of swampy depression and draining of stagnant water by channeling and excavation were carried out at 3 areas in Leyte, Philippines from 1974 to 1977. The change of snail population resulted in the land reclamation was evaluated by the methods previously developed by the population studies on this snail. As a result of statistical analysis based on y = log(x + 0.01) transformation and the antilogarithmic mean density A-y = (antilog -y) -0.01, the reduction of snail population was observed at 13 out of 18 sites studied at 3 project areas and the significant reduction was statistically confirmed at 9 sites of them. Particularly at Dagami area, which was a wide and heavily snail-infested land adjacent to Dagami Poblacion, the reduction rate of snail density reached 87.7% to 99.2% and some wet depressions have been converted into good rice fields with little snail infestation at the last survey.

Effect of some environmental factors on survival of overwintering mosquitoes, Culex pipiens pallens.

In connection with the possible overwintering of Japanese B encephalitis virus in mosquitoes, some experiments were carried out to examine the effect of temperature, day-length and blood feeding on the survival of the overwintering population of the mosquito, Culex pipiens pallens. No significant difference was observed in the survival rate between the blood-fed and unfed groups under a higher temperature (24 degrees C) and longer day-length (L:D 14:10). Under a lower temperature (16 degrees C) and shorter day-length (L:D 10:14), blood-fed mosquitoes survived twice as long as those under a higher temperature and longer day-length condition. Based on the analysis of wing-length distribution, it was clarified that the blood-fed mosquitoes were a uniform longer-winged group and that most of the shorter-winged mosquitoes were included in the unfed group. Judging from such lower blood-feeding activity of the shorter-winged mosquitoes, their survival rate is suggested to be low during or after overwintering.

Population studies on Oncomelania quadrasi, the snail intermediate host of Schistosoma japonicum, in the Philippines. 3. Data transformation for significance test of snail density.

For the comparative study of densities of Oncomelania quadrasi, the snail intermediate host of Schistosoma japonicum in the Philippines, the survey data should be transformed to stabilize the variance in determining the significant difference of densities among populations and to evaluate control measures by the difference, since the snail is distributed unevenly in the field. Comparison was made for the efficiency of stabilizing variance among 7 transformation formulas so far reported, and 2 new additional formulas in the present study. As a result, a simple transformation by y=log (x+0.01) was found to be most reliable. This nonparametric transformation can be applied to any snail population irrespective of the type of distribution and the degree of clumping. By this formula, there is no need to discard snail-free samples which are important to evaluate control measures. Using this transformation, snail survey data were analyzed in the areas where control measures were undertaken during the past several years. And significant reduction of snail densities was proven using the t-test.

Population studies on Oncomelania quadrasi, the snail intermediate host of Schistosoma japonicum, in the Philippines. 2. Necessary sample size for snail density survey.

In order to save time and manpower for the density surveys of Oncomelania quadrasi, the snail host of Schistosoma japonicum in the Philippines, the minimal necessary sample size (q) was determined using a formula, q greater than t2/E2(1d - 1 + 1/-x). This formula is based on the Id dispersion index [2, 3] which varies with the degree of clumping of unevenly distributed animals. A nomograph was prepared for the ready determination of the necessary sample size for various degrees of clumping (Id) and mean density (-x) to be encountered in the field. The reliability of the sampling procedure with an interval of 5 m distance, which has been adopted to the routine snail survey in the Philippines, was examined using the relative error (E). The relative errors calculated ranged below or around 20% (E = 0.2). Therefore, the existing sampling method was proven to be highly reliable as the field survey. Comparison was made between the sample size actually taken and the minimum needed theoretically determined by this method, by adopting the Student's t = 1 and relative error E = 0.3 as a permissible reliability level in the field. The actual sample size was more than twice the minimum needed for 21 out of 30 populations surveyed and less than the needed in 5 of the 30 surveys.

Population studies on Oncomelania quadrasi, the snail intermediate host of Schistosoma japonicum, in the Philippines. I. Distribution pattern of the snail in the field.

Distribution of Oncomelania quadrasi, the snail intermediate host of Schistosoma japonicum, was studied in Leyte, Philippines for the type of distribution based upon a large number of survey data. Among four distribution models examined, three uneven distribution models, i.e., the double Poisson, Neyman type A and negative binomial fitted well in this order but the Poisson model showed the poorest fitness. This indicates that the snails are distributed unevenly over the field and that the population mostly consists of small clusters of individual snails. Elucidation of the snail distribution pattern is necessary for determination of sample size in snail survey and for data transformation in significance test of the snail density comparison.