Liver changes in hamsters infected with a liver fluke of man, Opisthorchis viverrini.

Thirty male Syrian golden hamsters were each infected with 100 metacercariae of Opisthorchis viverrini. The hamsters were killed at 3, 7, 15, 30, 154 days of infection. The early pathological changes consisted of an acute inflammatory reaction involving the bile ducts of the second order and the portal connective tissue, especially the large veins, as well as focal coagulation necrosis of the liver lobules. As the flukes developed into adults they induced hyperplasia and adenomatous formations of the bile duct epithelium. There was also a granulomatous response to the adult flukes and eggs. Resolution of the granulomas led to periductal and portal scarring. These findings suggest that immunopathologic mechanisms may be important in the pathogenesis of liver fluke disease.

Morbidity in relation to intensity of infection in Opisthorchiasis viverrini: study of a community in Khon Kaen, Thailand.

A study of the prevalence and intensity of opisthorchiasis viverrini in relation to morbidity as determined by standard medical examination was carried out in Nong Ranya, a small village containing 309 people in northeastern Thailand. Opisthorchis viverrini infection as determined by Stoll's quantitative egg count method had an overall prevalence of 94% and reached 100% prevalence in most age groups above the age of 10 years. With respect to intensity, 6% were uninfected, 26% had light (less than or equal to 1 eggs per mg [epmg] of feces), 37% moderate (greater than 1-10 epmg), 25% heavy (greater than 10-50 epmg), and 5% very heavy (greater than 50 epmg) infections. Peak intensity in both males and females occurred at age 40 and above. A history of eating "koipla" (a sauce consisting of ground up raw fish), of feeling weak, and of having right upper quadrant abdominal pains occurred most frequently in the infected groups and was correlated with intensity of infection. Regardless of intensity of infection, only a small proportion of the population were unable to carry out their routine activities. Anorexia, nausea or vomiting bore little relationship to the presence or intensity of infection. Hepatomegaly at the mid-clavicular line occurred in 14% of the population, mainly in the more heavily infected groups. Neither jaundice nor splenomegaly was observed in the population.

Ancylostoma malayanum, Alessandrini, 1905 in Thailand.

Ancylostoma malayanum was recorded from a Malayan Sunbear, Helarctos malayanus, in Nakorn Sri Thammarat Province, Southern Thailand. Comparison of the body measurements recorded by various authors were presented. The morphological features were described and illustrated, including the anogenital papillae.

Prevalence and zoonotic potential of Ancylostoma ceylanicum in cats in Thailand.

Ancylostoma ceylanicum and Ancylostoma caninum were found in cats from Prachin Buri, Thailand, with infection rates of 92% and 23%, respectively. In this survey, 75% of cats were infected with A. ceylanicum alone, the rest had mixed infections of A. ceylanicum and A. caninum. The worm burden range in 26 cats for A. ceylanicum and A. caninum were 1 to 83 and 1 to 10, respectively. For A. ceylanicum, both males and females were found in the gut from the first part of duodenum to rectum. In the case of A. caninum the distribution was not constant. The sex ratio between male and female A. ceylanicum was 1:1.4. The egg count for A. ceylanicum was in the range 31-150 per gram of faeces (mean 70). The zoonotic potential of these parasites was discussed.

Electron microscopy of the advanced third-stage larvae of Gnathostoma spinigerum.

The morphological structures of the advanced third-stage larvae of Gnathostoma spinigerum are reported by using the scanning electron microscope. On the head-bulb, the larva bears two lateral lips, two labial papillae on each lip with an amphid between them. The head-bulb bears four transverse row of well-developed single-pointed hooklets. The number of the hooklets in each row increases posteriorly. The appearance of the hooklets by dorsal view and lateral view is also described. The whole body cuticle is transversely striated and covered with transverse rows of single-pointed spines which are dense on the anterior third of the body and became gradually less both in number and size towards the posterior extremity. The average number of transverse rows of these cuticular striations is 234. A pair of cervical papillae and an excretory pore are located on the anterior third of the body. A pair of body papillae is seen on the posterior half of the body. The subterminal anus is seen in the posterior extremity.

Humoral immune response of cats to Paragonimus infection.

The time course of humoral immune response to Paragonimus siamensis was studied in 10 cats experimentally infected with either 30 or 60 matacercariae and the antibody produced was detected by enzyme linked immunosorbent assay (ELISA), complement fixation test (CFT), and immunoelectrophoresis (IEP) test. With ELISA and CFT, antibodies was detected as early as 2nd week after infection and the cats remained positive throughout the 12 week period of observation. In contrast, the IEP test was persistently negative. With respect to sensitivity, both ELISA and CFT are equally sensitive but the mean ELISA titer was consistently higher than that of CFT. THe magnitude of the antibody response appeared to be related to duration of the infection but not to the infective dose and the number of worms recovered. There was variability in titers among cats infected with equal numbers of metacercariae. The tests can not be used for differential diagnosis of infections by P. siamensis and P. heterotremus because of the cross-reaction. Such cross-reaction did not not occur against unrelated parasites including hookworm. Toxocara cati and Spirometra mansoni.

Gnathostoma malaysiae Miyazaki and Dunn, 1965 from Rattus surifer in Thailand.

Gnathostoma malaysiae Miyazaki and Dunn, 1965 was found in the stomach wall of Rattus surifer, captured in Phuket Island and Khao Yai National Park of Thailand. This is the first to be recorded in Thailand and the second discovery after the first description of Miyazaki and Dunn (1965). Pathological findings of infected animals were also described. Some new morphological descriptions were added to the original.

Scrub typhus and chiggers in northern Thailand.

It was reconfirmed that L. deliense was the most dominant chigger during the rainy season in northern Thailand. Overall prevalence of IgG antibody against R. tsutsugamushi among the rural villagers in the northern most part of Thailand was nearly 60% at the level over 1 : 10 by an indirect immunofluorescent test. The level of IgG and IgM antibody titers was considerably high as greater than or equal to 1 : 2560 in some sera, but did not markedly vary by age groups or sexes. Based on detection of IgM antibody, the probability of new or reinfections were considered.

Control trial of soil-transmitted helminthic infections with pyrantel pamoate.

Pyrantel pamoate at dosage of 10 mg per kilogramme body weight was given to each villager at 4-6 weeks intervals for three times. The infection rates of hookworms among those who received and did not received the drug decreased from 60.5% pre-treatment to 19.6% after the third treatment and then increased to 32.4% one year after the third treatment. Infection rates of A. lumbricoides and Strongyloides spp. among the villagers who received and did not received the drug decreased from 27.5% pre-treatment to 2.2% after the third treatment and then increased to 20.1% one year later for the former, while the latter decreased from 6.5% pre-treatment to 2.3% after the third treatment and 0.4% one year later. The infection rate of T. trichiura was found to increase as pyrantel pamoate had no effect on this nematode. The authors suggested that to obtain more satisfactory results the anthelmintic drug used must likewise be effective against T. trichiura particularly in areas where this nematode is a public health problem. It was also suggested that the duration of treatment should be prolonged.

Evaluation of selected anthelmintic compounds for activity against Opisthorchis viverrini.

In vitro and in vivo experiments were employed in the screening of potential anthelmintic agents against Opisthorchis viverrini infection in hamsters. A few selected groups of compounds tested included those that are commercially available as well as those that are still being tested by various pharmaceutical firms. The compounds tested in the present study were praziquantel, amoscanate, albendazole, flubendazole, metrifonate, metronidazole and benzodiazepine derivatives. Results from both in vitro and in vivo experiments showed that at the dosages employed, praziquantel was the only one that gave complete cure, as judged from faecal egg examination and worm recovery at the time of sacrifice. It was therapeutically effective against different developmental stages of O. viverrini including the metacercariae. Moreover, the drug was also effective as a chemoprophylactic agent when given 6 to 12 hr prior to being exposed to infective metacercariae. Other compounds tested were considerably less active although some might have permanently damaged the fluke reproductive capacity, while others were able to suppress egg-laying capacity only temporarily. Together, results suggests that the ineffectiveness of most agents tested in this study is not related to their inability to attain concentrations high enough to kill or damage the flukes in the biliary system but is most likely due the inherent lack of capacity to kill the flukes.

Relationship between prevalence and intensity of Opisthorchis viverrini infection, and clinical symptoms and signs in a rural community in north-east Thailand.

In a large village in north-east Thailand, the overall prevalence of Opisthorchis viverrini infection (based on Stoll's quantitative egg count) was 89.5% in a total population of 1651 individuals. The prevalence was 32% in children under 5 years, 90% in those aged 5-9 years, and averaged 95.6% in age groups above 10 years. The mean faecal egg output (indicative of intensity of infection) was highest in the 40-49-year age group and remained relatively constant through older ages. In all age groups the prevalence and intensity of infection in both men and women were similar.A history of eating raw freshwater fish occurred more frequently in infected persons than in those uninfected. The following symptoms occurred significantly more frequently in groups with higher intensities of infection: weakness, flatulence or dyspepsia, and abdominal pain in the right upper quadrant. Nevertheless, infected persons did not report a reduced ability to work. Anorexia, nausea, vomiting, and diarrhoea were only weakly correlated with the intensity of infection. A palpable liver occurred more frequently in the infected groups and was correlated with intensity of infection. Icteric conjunctivae were observed in 2.2% of infected persons but not in the uninfected. Some 5-10% of the population had symptoms that were attributable to opisthorchiasis.