Giardia lamblia infections in Mongolian gerbils: an animal model.

Mongolian gerbils were susceptible to infection with Giardia lamblia cysts from patients. Inoculation of gerbils with 5 x 10(3) cysts each resulted in an infection characterized by the intermittent release of cysts for up to 39 days. The mean number of cysts released per gerbil in a 2-hr period was 8.8 x 10(2) (range, 0-5 x 10(3)). The highest number of trophozoites found in the intestine was on day 15 after infection, when the mean number of trophozoites per gerbil was 6.36 x 10(6). Administration of cysts from different patients to gerbils resulted in a similar pattern of cyst release during the first 30 days of infection. Mongolian gerbils were also susceptible to infection with cultured trophozoites (Portland 1 strain). The pattern of cyst release and the number of trophozoites in the intestines of orally and duodenally inoculated gerbils were similar. Gerbils were protected against reinfection with G. lamblia for up to eight months after primary infection.

The population biology and control of Ascaris lumbricoides in a rural community in Iran.

Adults of Ascaris lumbricoides were recovered from 252 persons in the village of Jazin near Esfahan, Iran after treatment with pyrantel pamoate. This horizontal study provides information on age-specific prevalence rates, intensities of infection, frequency distributions, sex ratios and eggs per gram of stool at different parasite intensities. Recruitment of A. lumbricoides was then monitored at 7, 30, 60, 90 and 365 days after treatment in 110 persons. A separate sample population was examined at monthly intervals and, in addition, the stool of each member of a nine-person family was examined for 10 consecutive days. These data are analysed and used to describe the dynamics of transmissions and recruitment of A. lumbricoides in Jazin. The population dynamics of ascariasis are discussed in the context of R the basic reproductive rate of the parasite. The relationships of R with frequency distributions, prevalencies and worm burdens are discussed. Because of the considerable potential of A. lumbricoides to re-infect man in endemic areas, it is shown that it will be difficult to eradicate ascariasis by the use of chemotherapy, even when drugs with a high efficacy are used repeatedly.

Gut propulsion in mice infected with Trichinella spiralis.

Previous investigators have shown that Trichinella spiralis increases intestinal motility and propulsion. We report here that primary infection with T. spiralis in the mouse increased gut propulsion, measured by the movement of nonabsorbable chromatography beads, on day 5 after infection but not 9 days after infection. Both cortisone acetate, an anti-inflammatory agent, and Lomotil, which reduced gut motility, could suppress the increase in gut propulsion seen 5 days after infection. The results suggest that early inflammation influences peristaltic activity and propulsion of intestinal contents.

Clinical changes caused by the liver fluke Metorchis conjunctus in cats.

Cats infected with metacercariae of the fluke Metorchis conjunctus were followed clinically through their infection. Cats given 200 metacercariae showed few symptoms. All the cats passed ova on the 17th day. Three hundred metacercariae caused diarrhea, icterus, discolored urine, green feces and eosinophilia after 18 to 21 days. Eosinophilia, leucine aminopeptidase and alanine aminotransferase were elevated and remain the best indicators for metorchiasis. The hematological and serological abnormalities resolved rapidly and were absent from cats with chronic infection. Acute lesions (less than 32 days) were confined to the biliary trees with extensive epithelial exfoliation, fibrosis, and pus from necrosis, tissue feeding by the worms and pressure atrophy. Chronic infections (32 to 150 days) caused hyperplasia of the bile epithelium, proliferation of connective tissues, and fibrosis of the perilobular areas. Intense eosinophilic infiltrates were replaced by mononuclear cells. Granuloma formation around an ovum was seen in one cat 719 days after infection. Adult worms established preferentially in the left lateral lobe and never in the caudal lobe. No gall bladder involvement was found even in heavy infections.

Wormy persons: contributions to the nature and patterns of overdispersion with Ascaris lumbricoides, Ancylosotma duodenale, Necator americanus and Trichuris trichiura.

The dominant intestinal helminths in the Iranian villages of Kargar Malleh (hookworms), Bandar Abbas (hookworms) and Jazin (Ascaris lumbricoides and Trichuris trichiura), were recorded with their frequency distributions, in 80, 40 and 111 villagers, respectively in 1977-78. Anthelminthics were then used to remove all intestinal stages which were identified and counted. Analyses showed clumped or over-dispersed patterns in all cases. Each community contained 'wormy persons', 1 to 3% of the individuals carried 11, 16, 30, 38 or 84% of all the worms collected. 'Wormy persons' could only be identified for one parasite, thus those with the highest infestations of one species were not prone to higher infestation with another. In Jazin, 111 persons with measured initial worm burdens of A. lumbricoides, T. trichiura and Trichostrongylus spp. were followed without further therapy or change in habits for up to 12 months during re-infection. There was no significant correlation between those persons with high initial worm burdens and those with high burdens after 12 months. The public health significance of these findings is discussed.

Intestinal parasites in man in Labrador, Canada.

Labrador, a previously unsurveyed area of Canada, has been sampled for human intestinal parasites. Four hundred and one asymptomatic volunteers between 1 and 72 years of age, including Inuit, Naskapi and whites, were examined during the summer of 1977. They harboured: Entamoeba coli, E. histolytica, E. hartmanni, Giardia lamblia and Diphyllobothrium sp. The infection rates are considerably lower than those found in other studies of Northern Canadian communities.

Comparative calorie values of nematodes.

Calorie values for a wide biological selection of nematodes, determined with a microbomb calorimeter, ranged from 3.86 to 6.85 Kcal/g. The mean of 5.095 Kcal from 16 species was lower than means recorded in three previous studies of other invertebrate groups. The nematode values were skewed to the lowest limit. Larvae of Ditylenchus dipsaci showed lower calorie values after storage, and the calorie values of separate tissues of Ascaris lumbricoides were highest for eggs and the intestine and lowest for cuticle and body-wall musculature. No clear calorie distinction exists between nematodes with a parasitic or free-living habit or between large and small nematodes.

Socio-agricultural factors and parasitic infections in the Caspian littoral region of Iran.

Surveys for intestinal parasites in villages in the Babol area of the Caspian littoral region of Iran have been conducted for five years. During this period, mass chemotherapy and individual treatment have been administered. While the overall prevalence of parasitic disease was reduced after these campaigns, reinfection took place repeatedly, and at a rapid rate. This paper re-examines the prevalence of seven helminth species (Ascaris lumbricoides), hookworms (Ancylostoma duodenale and Necator americanus), Hymenolepis nana, Strongyloides stercoralis, Taenia saginata, Trichostrongylus spp. and Trichuris trichiura) on the basis of geographical and socio-agricultural criteria. The considerable differences in the prevalence of these parasitoses--even between neighboring villages--emphasize the variability of human ecology in the region under study.

Parasitic disease in humans: the extent in Canada.

Much is being said, often dramatically, about the potential hazards of parasitic diseases in Canada, but little or no attempt has been made to determine the true extent of the problem. Indigenous parasite pathogens are recognized in resident Canadians, and pathogens are acquired by travellers abroad or reported from immigrants. The role of each of these categories is important in the characterization of the problem of parasitic diseases in Canada. From data provided by provincial laboratories and hospitals it is estimated that 1 person in 1000 will spend 1 day per year in hospital because of intestinal parasites, and 1 in 100 each year will have a diagnosis of intestinal parasitic infection made from examination of a stool sample.

Medical parasitology in China: an historical perspective.

Traditional Chinese anthelmintics prove to be interesting because social, political, cultural, psychological and philosophical factors could affect them. A review of the ideas on the origin of parasitic infection and the historical development of medical parasitology in China is attempted to aid in the elucidation of the rationale of traditional Chinese anthelminthic treatment.

Wave Forms of Caenorhabditis elegans in a Chemical Attractant and Repellent and in Thermal Gradients.

The wave forms and activity patterns of Caenorhabditis elegans were examined on agar in the presence of known chemical attractants (NaCl) and repellents (D-tryptophan), and in thermal gradients. Total activity was reduced in both attractants and repellents. Different combinations of transfers between chemicals were investigated. Two thresholds were found for NaCl: 10(-3) M NaC1 caused reduced activity; 10 M NaCl increased reversals. D- or L-tryptophan influenced neither orientation nor the ability of thermally acclimatized individuals to remain at their eccritic temperature.