Biomedical subjects

P C Fan

Publications and source records attributed to P C Fan.

At least 19 recordsLinked to original sources

PubMed2006

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.

Animals↗

PubMed2005

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.

Animals↗

PubMed2005

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.

Animals↗

PubMed2003

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).

Animals↗

PubMed2002

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.

Animals↗

PubMed2001

Parasitic infections among the aborigines in Taiwan with special emphasis on Taeniasis asiatica.

According to the results obtained by our laboratory and the Department of Parasitology, Taipei Medical College, from 1995 to 1998, the overall infection rate of enterobiasis was 16% (4-29%) among 4,426 primary school students at 64 schools in 13 mountainous districts of 10 counties, and the infection rate of head louse infestation was 12% (3-26%) among 5,121 students. A continuous series of field studies on epidemiology and chemotherapy of taeniasis asiatica have been conducted between 1971 and 1992 among 27,359 aborigines in 88 villages of 14 districts in 10 counties and 3,104 were found to be infected, giving an overall infection rate of 11%. Laboratory studies have been performed on the morphology, intermediate hosts, experimental infection, immunology and molecular biology. Moreover, development of Taiwan Taenia in one of 3 volunteers has been successfully demonstrated since 1988. Moreover, the domestic pig was identified as the intermediate host of Taiwan Taenia as in the classical T. saginata (Poland strain). Most of cysticerci were developed in or on the parenchyma of liver. The results indicated that Taiwan Taenia is different from classical T. saginata. It has been named as T. s. asiatica. Moreover, the classical T. saginata was renamed as T. s. saginata. This paper summarizes findings and reviews those reported by our laboratory. In addition, the clinical manifestations and eating habits of the aborigines are also discussed.

Child↗

PubMed2001

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.

Animals↗

PubMed2001

Experimental studies on physiological and morphological aspects of Cysticercus cellulosae in pigs.

Three Small-Ear-Miniature, 3 Landrace-Small-Ear-Miniature, and one Douc-Yorkshire-Landrace pigs were inoculated orally with 100 000 eggs of Zhengzhou strain or 10 000 eggs of Harbin strain of Taenia solium. A total of 3739 cysticerci were recovered from 3 Small-Ear-Miniature and 3 Landrace-Small-Ear-Miniature pigs, giving an infection rate of 85.7% and a cysticercus recovery rate of 1.1%. The predilection sites of Cysticercus cellulosae in descending order were leg muscles, abdominal muscles, thoracic muscles, liver, head muscles, diaphragm, tongue, heart, trachea, and omentum/testes. Except 2 calcified cysticerci in the tongue, 2 in the heart, and 176 in the liver, the remaining cysticerci were all alive. The greatest number of cysticerci per 100 g of muscles or viscera was found in the head muscles, followed by the leg, diaphragm, heart, tongue, thoracic, abdominal, omentum, testes, and trachea. All cysticerci were evaginated in pig's bile after fluid was drawn out from cysticerci, whereas evagination occurred in only 83.2% of those without fluid drawing. In 364 evaginated cysticerci, the mean length and width of scolex, proglottid, and bladder, and diameter of rostellum and sucker were 826 x 747 microm, 5,370 x 1,734 microm, 2,885 x 3,002 microm, 155 microm, and 253 microm, respectively. In the protoscolex, the mean number of segments was 33. Each cysticercus had 2 rows of rostellar hooks on the scolex, and the mean length and width of inner and outer hooks were 151 x 18 microm and 117 x 14 microm, respectively. The number of paired hooks ranged from 10 to 18.

Animals↗

PubMed2001

Current status of imported parasitic infection among foreign workers in northern Taiwan (1999-2000).

In the present study, a simple, economic and practical technique was employed for stool examination. Of a total of 6,146 fecal samples from foreign workers in Northern Taiwan between 1999 and 2000 were examined, 615 were found to be positive for parasitic infection and the overall infection rate was 10%. Newly arriving foreign workers had a significantly higher infection rate (15%) than those who had worked in Taiwan for 6-12 months (8%). The foreign workers came from Indonesia, Philippines, Thailand, Malaysia, and Vietnam. Except for the small number of workers from Malaysia which was not included, the infection rate order by nationality was Vietnamese (21%) > Indonesian (13%) > Philippino (10%) > Thai (4%). The female examined workers were about 3-fold of males and their infection rate (11%) was also significantly higher than the males (5%). The order of rates by age was 20-30 years (11%) > 31-40 years (8%) > 41-50 years (5%). According to the species of parasites, 569 foreign workers were infected with 1 species (9%) > with 2 species (0.7%) > with 3 species (0.1%). Totally, 14 species (10 helminths including 1 plant nematode, Heterodera and 4 protozoa; hookworm might include 2 or 3 species, but counted as one species here) were found, of which 10 species were pathogenic (9 helminths and 1 protozoa) and 4 non-pathogenic. Foreign workers from Indonesia harbored 12 species of parasites > from the Philippines, 9 species > from Thailand, 8 species > from Vietnam, 7 species.

Adult↗

PubMed2001

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.

Animals↗

PubMed2000

Rodent model for long-term maintenance and development of the viable cysticerci of Taenia saginata asiatica.

Although oncospheres of Taenia saginata asiatica can develop into cysticerci in immunodeficiency, immunosuppressed, and normal mice, no detailed information on the development features of these cysticerci from SCID mice is available. In the present study, the tumor-like cyst was found in the subcutaneous tissues of each of 10 SCID mice after 38-244 days inoculation with 39,000 oncospheres of T. s. asiatica. These cysts weighed 2.0-9.6 gm and were 1.5-4.3 cm in diameter. The number of cysticerci were collected from these cysts ranged from 125 to 1,794 and the cysticercus recovery rate from 0.3% to 4.6%. All cysticerci were viable with a diameter of 1-6 mm and 9 abnormal ones each with 2 evaginated protoscoleces were also found. The mean length and width of scolex, protoscolex, and bladder were 477 x 558, 756 x 727, and 1,586 x 1,615 microns, respectively. The diameters of suckers and rostellum were 220 microns and 70 microns, respectively. All cysticerci had two rows of rostellar hooks. These findings suggest that the SCID mouse model can be employed as a tool for long-term maintenance of the biological materials for advanced studies of immunodiagnosis, vaccine development, and evaluation of cestocidal drugs which would be most benefit for the good health of the livestocks.

Animals↗

PubMed2000

Capillaria hepatica: a spurious case with a brief review.

A 12-year-old Bunun aboriginal school student in Sanmin District Kaohsiung County, Southern Taiwan, was found to have Capillaria hepatica eggs in the feces during a survey on intestinal parasitic infection in 1997. Moreover, this student was also infected with Trichuris trichiura and Ascaris lumbricoides. The C. hepatica eggs were light yellowish-brown in color, 54 (40-60) microns in length and 29 (25-35) microns in width with a 3 (3-4) microns thick shell and two colorless egg plugs 7 (5-9) x 6 (5-8) microns. This is the eighth case of human spurious C. hepatica infection in Taiwan. In addition to the reporting of this case, the genuine and spurious infections of C. hepatica in humans as well as its infection in rats around the world are briefly reviewed.

Adolescent↗

PubMed1999

Oncospheres of Taenia solium and T. saginata asiatica develop into metacestodes in normal and immunosuppressed mice.

Normal and immunosuppressed mice were infected with oncospheres of Taenia saginata asiatica and T. solium. Although normal ICR mice were not susceptible to these two parasites, cysticerci were recovered from the immunosuppressed ones following venous injection. For T. s. asiatica, immunosuppressed ICR mice had an infection rate of 12.5% and six cysticerci of this parasite were recovered from three males. After injection of T. solium oncospheres, a high infection rate of 57% was obtained and 23 cysticerci were collected from 13 male immunosuppressed ICR mice. The immunosuppressed C57 mice had the highest infection rate (100%) and cysticercus recovery rate (2.4%) for T. solium. The infection rate and cysticercus recovery rate in six normal C57 mice were 40% and 3% respectively. The immunosuppressed ICR, Balb/c and C3H mice were also susceptible to T. s. asiatica.

Animals↗

PubMed1999

Prevalence and treatment of Pediculus capitis infestation among aboriginal school children in northern Taiwan.

In the present study, pediculosis was investigated among a total of 2,725 children from 35 primary schools in Hsiulin District of Hualien County, Jenai District of Nantou County, Wulai District of Taipei County, Chienshih District of Hsinchu County, Fushing District of Taoyuan County, and Nanao District of Ilan County. The overall infestation rate was 12.8%. The rates by districts were 19.7%, 17.3%, 16.7%, 15.1%, 7.9%, and 3.0%, respectively. The pediculicides including Nix (permethrin 1%) 56 gm/tube, Para aerosol (bioallethrin 0.66%) 90 gm/tube, and Perioderm (malathion 1%) cream shampoo 40 gm/tube were used to treat the head louse infestation in 83, 91, and 103 children; the cure rates were 97.3%, 94.1%, and 93.4%, respectively. No significant differences were found in these rates. The reactions were slight and transitory. A total of 636 lice was collected from the hair using fine-toothed combs before treatment and from the used towels after treatment of children in Wulai, Chienshih, Hsiulin, and Jenai Districts. Each child was found infested with a mean of 7.7 lice. The mean intensity of infestation was highest in Jenai (9.3) and Chienshih (8.7) came next. Wulai (3.7) and Hsiulin (3.6) had lower intensities.

Animals↗

PubMed1999

Sexual development of Taenia solium in hamsters from rodent-derived cysticerci.

In order to determine whether Taenia solium can be maintained in the laboratory using rodents as definitive hosts, six nude rats, 20 immunosuppressed Mongolian gerbils and 20 immunosuppressed Syrian hamsters were each inoculated through a stomach tube with three cysticerci recovered from SCID mice. No adult worms of T. solium were found in the intestinal tract of any of these 46 rodents. In addition, five immunosuppressed Syrian hamsters were fed with the same number of cysticerci enclosed in rodent muscles from SCID mice. Two of these hamsters were found to be infected 40 days post-infection, each harbouring a sexually developed worm in the intestinal tract. Although no eggs were produced, prepatent infections may be possible if a longer time was allowed for worm development. Moreover, the maintenance of the life cycle of T. solium in the laboratory using the rodent model can be established.

Animals↗

PubMed1998

Viability of metacercariae of Clonorchis sinensis in frozen or salted freshwater fish.

Metacercariae of Clonorchis sinensis were collected from freshwater fish (Pseudorasbora parva) after storage in a freezer at -12 degrees C for 10-20 days, in a freezer at -20 degrees for 3-7 days, or treating with heavy salt (fish/salt = 10 gm/3 gm) at 26 degrees for 5-15 days. The metacercariae from the frozen fish were inoculated into 30 rats and eight rabbits, and those from the salted fish into 33 rats. Metacercariae from freshwater fish stored at -12 degrees for 10-18 days or -20 degrees for 3-7 remained viable and infective. Moreover, those kept at the heavy salt concentration for 5-7 days remained viable and infective. These findings indicate that freezing or storing infected freshwater fish in heavy salt may not be effective in the prevention of clonorchiasis. However, it appears that refrigeration, or keeping the fish in salt for longer periods, may be suitable for prevention of the infection.

Animals↗

PubMed1998

Review of enterobiasis in Taiwan and offshore islands.

From 1995 to 1997, we carried out extensive surveys of Enterobius vermicularis infection among school children in Taiwan and offshore islands. Among 6,315 children at 80 schools in 21 towns and districts of 8 counties tested, an overall infection rate was 11%. The pre-school children had the highest rate of 14%. These findings indicate that pinworm infection remains highly prevalent in Taiwan and offshore islands. Moreover, in this paper, the results from the studies conducted by parasitologists of Taiwan in the past 43 (1955-1997) years were reviewed. This information included epidemiology, diagnosis, chemotherapy, and control methods, may provide some useful suggestions on the prevention of pinworm infection specialists and agencies concerned with the control of this disease.

Adolescent↗

PubMed1998

Taenia saginata asiatica: epidemiology, infection, immunological and molecular studies.

The taeniasis in East Asia has a special epidemiological pattern: people eat meat and/or viscera of pigs and acquire infection of Taenia saginata-like tapeworms. However, cysticercosis is more often found in pigs than cattles. In order to elucidate the taxonomic status of this parasite, we have conducted extensive field surveys, experimental infections, and morphological as well as immunological studies since 1981. After obtaining sufficient information from our studies, we finally came to the conclusion that the T. saginata-like tapeworm in Asia is a new subspecies of T. saginata and was named as T. saginata asiatica. The classical T. saginata was renamed as T. saginata saginata. In this paper, we provide the history of T. s. asiatica in Asia.

Animals↗