Study of the morphological characteristics of Schistosoma mansoni in mice, squirrels, and hamsters.

This study attempted to describe mophological characteristics of S. mansoni worms. In the present study, 6 hamsters, 35 squirrels and 141 mice were infected with pooled cercariae of Schistosoma mansoni by intraperitoneal and percutaneous routes. The worm recovery rate was 18.2% (257/1,412) in hamsters (Mesocricetus auratus); 10.1% (3,310/32,792) in squirrels (Callosciurus erythraeus roberti) and 16.2% (4,328/26,720) in mice (Swiss strain). There were no significant differences between the sizes of 332 adults studied from three kinds of experimental animals. However, the worms collected from the hepatic portal system were usually larger than those from the peritoneal cavity because the latter almost always remained in the immature stage. We found male S. mansoni with tandem (17-22%), non-tandem (80-83%) and unusual/irregular arrangement (3-5%) of testes. The number of S. mansoni testes found were from 3 to 15 in mice, 3 to 11 in hamsters and 4 to 15 in squirrels. Mature worms had a tendency to reduce their size with aging. The number of S. mansoni cecal loops were from 1 to 5 in mice and hamsters and 1 to 4 in squirrels. The location of the first cecal loop was usually in the anterior part of body (1/4 in females and 1/3 in males), but there were some exceptions. The number of eggs in the uterus of each female worm, were 0-3 in mice, 0-1 in squirrels and hamsters. The average number was 0.75. The location of the ovary was usually situated in the anterior part of body of the worm in the three kinds of experimental animals. A few mated male and female worms of S. mansoni being free in the peritoneal cavity were found to develop to sexual maturity, because eggs were observed in their uteri. Their size was usually found to be considerably smaller than the worms seen in the hepatic portal system, and they had no hematin in their intestinal ceca. Encapsulated eggs were found from the peritoneal cavities of a few mice following intraperitoneal and percutaneous methods of infection.

Cysticercosis in Domestic Animals and Rodents / 中国人兽共患病学报

Cysticercus cellulosae, C. bovis, and C. taiwanensis are the three species of cysticercosis of human taeniid with their adults worms Taenia solium, T. saginata saginata and T. s. asiatica respectively. C. cellulosae is prevalent in America, Europe and Asia, C. bovis in Africa, America and Asia and C. taiwanensis in Asia. The natural infection source is pig for C. cellulosae, cattle for C. bovis and pig and wild boar for C. taiwanensis. The predilection sites are muscles for C. cellulosae and C. bovis and liver for C. taiwanensis. While the prepatent periods of these three species were 60-70 days, 60-75 days and 28 days respectively. Most C. cellulosae and a few for C. bovis and C. taiwanensis survive in pig, while most C. bovis and a few for C. taiwanensis survive in cattle. In rodent, all three species have a long life. C. cellulosae and C. bovis migrate through blood and lymph vessels to the small intestinal wall and then to the body muscles while C. taiwanensis migrate through blood vessels to the small intestinal wall and then to the liver. The minimal effective dosage of praziquantel against cysticercosis should be 100 mg/kg daily for three consecutive days.

Hybridization of Schistosoma mansoni and Schistosoma japonicum in mice.

Crossing experiments in mice with two human species of Schistosoma japonicum (Taiwan strain) and Schistosoma mansoni (Puerto Rican strain) were performed. The hybrid miracidia from the cross between female S. japonicum and male S. mansoni infected both Biophalaria glabrata and Oncomalania h. chiui. However, those from the reciprocal crossing could infect only B. glabrata. B. glabrata infected with hybrid miracidia of female S. mansoni x male S. japonicum survived up to 30 days while those infected with miracidia of S. mansoni remained alive for more than 100 days after the first shedding of cercariae. Relatively few hybrid eggs reached maturity either in tissues or in the feces of infected mice. A low percentage of F1 eggs hatched and the infectivity of F1 miracida was also low. Morphology and behavior of hybrid eggs, miracidia, cercariae, and adults were similar to the maternal species. The daily egg production of the hybrid worm pair was less than that of the normal one. The observations in the present study may be attributed to the maternal effects. However, the phenomenon of parthenogenesis in schistosomes cannot be confirmed.

Infectivity and development of the human strain of Hymenolepis nana in ICR mice.

In order to study the infectivity and development of the human strain of Hymenolepis nana in mice, a human strain of H. nana was inoculated into ICR mice. H. nana eggs were concentrated by the sedimentation method and inoculated by a disposable syringe (1 ml) connected to a long needle (8 cm) into the stomach of mice. Mouse feces were examined daily beginning day 5 after inoculation and the mice were sacrificed from days 19 to 65 post-infection (PI). The infection rate and worm recovery rate were 69% and 17%, respectively. The prepatent period ranged from 7 to 23 days. Autoinfection was found to occur in an ICR mouse infected with 60 eggs; 102 worms were recovered from its small intestinal lumen on day 19 PI. One row of hooklets was found on the scolex and the mean number of hooks was 19. The average length, width, and number of segments were 51 mm, 0.6 mm, and 1,099, respectively. The mean length and number of immature segments were 9 mm and 414 segments, mature segments 20 mm and 390 segments, and gravid segments 22 mm and 295 segments. The average length, width, and number of segments in 26 autoinfected worms were 11.5 mm, 0.3 mm, and 189 segments. The mean length and number of immature segments were 3.9 mm and 41 segments, mature segments 4.4 mm and 65 segments, and gravid segments 3.2 mm and 83 segments, respectively.

Egg production capacity of one-pair worms of Schistosoma japonicum in albino mice.

In the present study, a series of procedures of egg count were carried out to determine the egg production capacity in 21 ICR mice each infected with one-pair of Schistosoma japonicum. The egg count began from the first day, they were detected in the feces, which was based on a stool collection over 24 hours, twice a week. Each female S. japonicum produced an average of 2,198 eggs/day during the study period of 99 days after infection (ranged 61-147 days). Fourty-seven percent of the eggs were in the feces and 53% in tissues (45% in large intestine, 31% in small intestine, 23% in liver, 0.4% in pancreas, 0.2% in lungs, 0.1% in spleen, 0.1% in lymph nodes, 0.06% in stomach and 0.05% in heart, kidney, diaphragm and brain).

A sieving method for collecting the metacercariae of trematode parasites from freshwater fish.

This study describes a sieving method for the collection of metacercariae from frozen (-20 degrees C) freshwater fish. Digested fish tissue is filtered through a series of sieves; the crude filtrate is then centrifuged. Centrifugation produces a sediment from which metacercariae can be removed. Half of the metracercariae that were obtained from the fish meat that had been frozen for 10 days (-20 degrees C) were dead; the other half were alive and some larvae were moving slowly.

Experimental studies on small hooks preceding large hooks in the growth and development of Taenia solium metacestodes.

In the present study, we have determined the growth and development pattern of rostellar hooklets of Taenia solium cysticerci (Zhengzhou and Harbin strains) in three pigs (1 SEM and 2 L-SEM strains) 89-196 days post experimental infection. A total of 3,675 cysticerci were collected from 3 pigs, 3,007 (82%) of 3,675 cysticerci were evaginated by enzyme method. 439 (15%) evaginated cysticerci were carefully examined and measured after dehydration, staining, and mounting on microscopic slides. Among 439 cysticerci, 234 (53%) had pair rostellar hooks, 88 (20%) with unpair hooks, 60 (14%) only small (outer row) hooks, and 57 (13%) no hooks including 34 hooks were completely dropped and 23 no hooks developed. The number ranged from 10 to 17 pairs for pair hooks and 1 to 29 for unpair ones. The length and width of rostallar hooks on the scolex of cysticerci were usually larger in the pig with longer infection time. Moreover, cysticerci with pair and unpair rostellar hooks had only small hooks and no hooks were present on their scolices. However, cysticerci with only large (inner row) hooks were not found. These findings indicate that the growth and development of small hooks precedes that of the large hooks in the formation of the two-row pattern rostellar hook in Cysticercus cellulosae.

Studies on abnormality of metacestodes and adult worms of Taenia solium and Taenia saginata asiatica in rodents and pigs.

Abnormalities are not uncommon in Taenia saginata and T. solium. After examining 328 mature proglottids from 2 adult worms from two experimentally infected hamsters, 13 (4.0%) were found to have no genital pore but with numerous testes and several vas efferents; 1 (0.3%) one genital pore with one reproductive system; 12 (3.7%) one on each side with two sets of reproductive system; 17 (5.2%) two on one side with 2 sets of reproductive system; 8 (2.4%) one on one side and two on the other side with 3 sets of reproductive system; 2 (0.6%) two on each side with 4 sets of reproductive system; 4 (1.2%) three on one side with 3 sets of reproductive system, and 4 one on one side and three on the other side with 4 sets of reproductive system. Nine evaginated abnormal cysticerci of T. s. asiatica from three experimentally infected SCID mice each had two protoscoleces and a big bladder. From two experimentally infected pigs, one abnormal cysticercus was observed to have two invaginated canals each in one end. Another one had a neck-band behind the scolex and a big bladder. This paper is not only the first report of abnormality of T. solium from hamster but also the first one of abnormal cysticerci of T. s. asiatica from pigs and mice.

Annual economic loss caused by Taenia saginata asiatica taeniasis in three endemic areas of east Asia.

The Taenia saginata-like tapeworm in East Asia has been designed as a separate subspecies of T. saginata. It was named as T. saginata asiatica and the classical T. saginata as T. saginata saginata. In the course of conducting experimental infections and morphological studies, a large number of adult worms of T. saginata asiatica was collected. It is possible to estimate the annual economic loss caused by this infection, since the worm load and the weight of worm habored by each infected person were determined from the collection. In the mountainous areas of Taiwan, the infection rate of T. saginata asiatica taeniasis was 11.0%, the worm load was 1.6 worms/case, and the average weight of an adult worm was 20.5 g. The annual economic loss was estimated to be US$ 11,327,423. On Cheju Island of Korea, the infection rate was 6.0%, the worm load was 2 worms/case, and the average weight of an adult worm was 19.3 g. The annual economic loss was estimated to be US$ 13,641,021. On Samosir Island of Indonesia, the infection rate was 21%, the worm load was 1.8 worms/case, and the average weight of an adult worm was 22 g. The annual economic loss was estimated to be US$ 2,425,500. These figures indicate that taeniasis is not only a significant public health problem but also an important economic problem in East Asia.

Asian Taenia saginata: species or strain?

Asian Taenia has a special epidemiological pattern. Many people eat raw and/or undercooked pork and pig viscera more often than that of cattle and acquire a T. saginata-like tapeworm infection. The pig has been found to be the most favorable laboratory intermediate host for four geographical strains of Asian Taenia. Numerous pinpoint cysticerci have been found in naturally infected livers of one wild boar and six domestic pigs in Taiwan. It is likely that pigs are the natural intermediate host of Asian Taenia in endemic areas other than Taiwan. Moreover, the cysticerci of Asian Taenia are only found in the livers of the infected animals and have similar morphological characteristics, which are distinguishable from the cysticerci of T. saginata and T. solium. These cysticerci are small in size and armed with two rows of rudimentary hooklets and can develop to maturity in as short a period as 4 weeks. It is possible that Asian Taenia is a different species or at least a different strain.

Laboratory transmission of lymphatic filariasis by vector mosquitoes.

Aedes togoi and Ae. aegypti were used to examine the transmission potential of Brugia pahangi to one of its natural hosts, the domestic cat. Although a larger proportion of microfilariae taken in by Ae. togoi developed into infective larvae, the total number of B. pahangi larvae recovered from a cat exposed to Ae. aegypti was larger than from a cat exposed to Ae. togoi. Factors influencing the transmission dynamics included: development of microfilariae to infective larvae; survival of mosquitoes; willingness to take repeated blood meals; and proportion of infective larvae that egress from mosquitoes during the feeding process. From 19 to 25% of infective larvae were transferred to a susceptible host. The feasibility of using a Brugia-cat model to do comparative vector efficiency studies was demonstrated.

Studies on taeniasis in Taiwan. V. Field trial on evaluation of therapeutic efficacy of mebendazole and praziquantel against taeniasis.

Taeniasis is a major public health problem among the aboriginal populations on Taiwan, and is highly prevalent and wide spread in the mountain areas of 10 Counties. Over 27,000 cases of tapeworm infection are estimated influencing the health and economy in the endemic areas. A treatment of taeniasis with mebendazole and praziquantel followed by a re-treatment with atabrine has been done in the field trial, and confirmed that praziquantel is highly effective agent against tapeworm infection, but mebendazole is not. Based upon experiments reported here praziquantel in a single dose of 150 mg, and 450 mg are highly effective against taeniasis and hymenolepiasis respectively.

Experimental infection of subperiodic Brugia malayi in laboratory rats with emphasis on evaluation by four techniques.

Infective larvae of subperiodic B. malayi from South Kalimantan (Borneo), Indonesia collected from laboratory-raised Ae. togoi mosquitoes after feeding on infected mongolian gerbils (Meriones unguiculatus) were inoculated subcutaneously into the groin areas of 15 SD and 36 LE rats. Blood was examined weekly by membrane filtration and thick smears starting 10 weeks post-infection. Microfilariae were found in 3 SD and 4 LE rats, the mf infection rate of 20% and 11% respectively. The prepatent period was significantly shorter in the SD rats (99-112 days) than those in the LE rats (110-153 days). The patent period was longer in the LE rats (208-703 days) than in the SD rats (236-543 days), and the mf density was similar (17.5 mf/20 c.mm blood against 16 mf/20 c.mm blood). At necropsy, 6 (3 female and 3 male) adult worms were recovered from 3 of 6 SD rats and 12 (9 female and 3 male) adult worms from 4 of 20 LE rats; all worms were found in the testes. The results of xenodiagnostic, histochemical staining and measuring spicules and protuberances, demonstrated clearly the difference between both species of Brugia. All dissected Ar. subalbatus mosquitoes exposed to B. pahangi became infected (100%), but none of those to subperiodic B. malayi were infected (0%). The mf of both species of Brugia in thick films stained with naphthol-AS-TR-phosphate showed that the excretory and anal pores of subperiodic B. malayi mf exhibited acid phosphatase activity and only a little activity was seen in other parts; while B. pahangi mf showed heavy diffuse acid phosphatase activity along the entire length of the body.(ABSTRACT TRUNCATED AT 250 WORDS)

Medically important snails of Kinmen (Quemoy) Islands.

A survey and collection of the snails of medical importance were conducted in June, 1980 on Kinmen Islands. More than 2,700 snails were collected from 23 different localities. They were preserved, carefully classified, and compared in habitat distribution with snails of Taiwan. A total of fourteen species of snails was found. This study has led to the establishment of snail fauna of Kinmen. The relationships of these snails with some snail-borne diseases are discussed.

Studies on the susceptibility of new Taiwan foci of Oncomelania hupensis to Ilan and Japanese strains of Schistosoma japonicum.

Sixty snails from four new foci of O. hupensis in Taitung, Chiayi, Hualien and Nantou counties, and 4 known colonies of O. h. chiui in Alilao and Pali in Taipei as well as of O. h. formosana in Changhua and Ilan on Taiwan were exposed each to 5 miracidia of Ilan zoophilic strain and Japanese anthropophilic or human strain of S. japonicum. This is the first report to note that all four new foci of O. hupensis snails were highly susceptible to Ilan strain of S. japonicum (17-20%). Susceptibility to the Japanese strain was detected in Taitung (33%), but, very low to not susceptible for the Hualien (2%), Chiayi and Nantou snails. Susceptibility of new Taiwan foci to the geographic strains of S. japonicum has now been well established, widespread distribution of susceptible snails in Taiwan could possibly lead to public health problem in the event that S. japonicum were introduced to the island.

Further studies on the susceptibility of new Taiwan foci of Oncomelania hupensis to geographic strains of Schistosoma japonicum.

Two known colonies of O.h chiui in Alilao and of O.h. formosana in Changhua and four new foci of snails in Nantou, Chiayi, Hualien and Taitung on Taiwan were exposed each to 5 miracidia of Changhua Zoophilic strain and Chinese, Philippine and Indonesian anthropopilic or human strains of S. Japonicum. The results showed that all four new foci demonstrated various degrees of susceptibility to this parasite. Infectivity of Chinese strain of S. japonicum in 4 new foci of snails is reported for the first time. Changhua race of O. hupensis was also found slightly susceptible to Chinese strain of the parasite. The average infection rate to both zoophilic and human strains of S. japonicum was 39.0%, 14.5%, 10.8% and 9.8% for Taitung, Chiayi, Hualien and Nantou snails respectively. Susceptible snails now been found in 7 counties and if by chance human pathogenic strains of the parasite were accidentally introduced into Taiwan, a public health problem could possibly develop.

The effect of diethylcarbamazine treatment on the development of bancroftian microfilariae in Culex p. fatigans.

Bancroftian microfilarie survived after one to three courses of diethylcarbamazine treatment in carriers and the larvae able to reach the infective stage in Culex p. fatigans. The infection rate and the development of infective larvae per infected mosquito from DEC-treated carriers was much lower than from the untreated carrier. The fact that surving MF can develop to infective stage in their vector indicates that such filarial carriers may be important sources for transmission of filariasis in the endemic areas after suspension of control measures.