Interrelationship between diarrhea and vitamin A deficiency: is vitamin A deficiency a risk factor for diarrhea?

A cross-sectional study, a follow-up study and an evaluation of impact of community-based distribution of vitamin A capsules (200,000 IU) were conducted in Omdurman (Sudan) between November, 1988, and March, 1989. In the cross-sectional survey 1441 children less than 5 years of age participated, which established the baseline values for plasma retinol-binding protein. During the follow-up period 290 cases of diarrhea occurred. Low concentrations of plasma retinol-binding protein (less than 1.85 mg/dl) proved to be a risk factor for diarrhea, especially in girls. The relative risk increased after the second year of life. Children who received vitamin A supplementation before commencement of the study had a lower incidence of diarrhea. The protective effect of vitamin A supplementation was greater in girls (relative risk, 0.297; 95% confidence interval, 0.240 to 0.368) than in boys (relative risk, 0.404; 95% confidence interval, 0.352 to 0.464).

Onchocerciasis in a California dog.

A 15-year-old dog that had lived all of its life on ranches and at the Wildlife Waystation on the western edge of the San Gabriel mountains near Los Angeles, California, developed an extensive granulomatous lesion involving the right eye and associated tissues requiring removal of both the eye and the lesion. Microscopic examinations of the tissues revealed the presence of living and dead gravid female worms and male worms belonging to the genus Onchocerca. Unsheathed microfilariae presumed to be Onchocerca species were found in the skin as well. Because Onchocerca species are not natural parasites of dogs, it is presumed that this infection was acquired accidentally from bovine, equine, or other animal host sharing the environment. This appears to be the first published record of patent onchocerciasis in a dog.

Therapy for human gastrointestinal microsporidiosis.

Gastrointestinal microsporidiosis is a major cause of diarrhea and wasting in persons with acquired immune deficiency syndrome (AIDS). Microsporidia demonstrate properties of both true eukaryotes and prokaryotes. The biology of microsporidia makes its elimination from the gastrointestinal tract therapeutically challenging. This organism depends greatly on the host for its energy needs and reproduction; microsporidial spores are impervious to the elements. Microsporidial infection of the gastrointestinal tract, principally with Enterocytozoon bieneusi and Encephalitozoon intestinalis in patients with AIDS has been treated with different medical regimens with variable success. The less common pathogen, E. intestinalis, responds well to albendazole, making it excellent first-line therapy, but such is not the case for E. bieneusi. None of the benzimidazoles has been demonstrated to be efficacious for E. bieneusi. On the other hand, E. bieneusi has shown excellent clinical therapeutic response to either direct action with fumagillin or its analogue, TNP-470, or indirectly by immune enhancement by suppression of the HIV virus with more aggressive, highly effective antiretroviral therapy. Further work is necessary to fully establish proper therapeutic protocols and manage side effects of the treatments. Other promising forms of therapy such as polyamine inhibitors and thalidomide demonstrate certain effectiveness in treatment of microsporidian in vitro (polyamine inhibitors) and in selected cases in vivo (thalidomide). Lack of either sufficiently suggestive or definitive human studies prevents the endorsement of these modes of therapy for treatment of gastrointestinal microsporidiosis at this time.

First report of Angiostrongylus cantonensis in Puerto Rico.

From January to April 1984, 63 Rattus rattus and 40 R. norvegicus were trapped in northeastern Puerto Rico and examined for Angiostrongylus cantonensis adults. Nineteen (47.5%) of the R. norvegicus and 10 (15.9%) of the R. rattus were infected, giving an overall infection rate of 28.2%. Four species of terrestrial snails and one species of brown slug were examined for A. cantonensis larvae. Two snail species, Subulina octona and Aquebana belutina, were found infected with third stage larvae of A. cantonensis. These larvae were harvested and inoculated per os into adult white mice. Immature adult worms were found in the brain tissue of all mice inoculated. This is the first report in the rat and snail populations of Puerto Rico.

Epidemiology of isosporiasis among persons with acquired immunodeficiency syndrome in Los Angeles County.

To determine factors associated with isosporiasis in persons with acquired immunodeficiency syndrome (AIDS) in Los Angeles County, data from the AIDS surveillance registry were analyzed for the eight-year period 1985-1992. Isosporiasis was reported in 127 (1.0%) of 16,351 persons with AIDS during the study period. Prevalence of infection was highest among foreign-born patients (3.2%), especially those from El Salvador (7.4%) and Mexico (5.4%), and in all persons of Hispanic ethnicity (2.9%). Persons with a history of Pneumocystis carinii pneumonia (PCP) were less likely than PCP-negative patients to have isosporiasis (0.2% and 1.4%, respectively, P < 0.01). A decrease in the prevalence of isosporiasis in patients negative for PCP was observed beginning in 1989 (P = 0.02). Prevalence decreased with age (P < 0.01, by chi-square test for trend). After controlling for multiple factors by logistic regression, isosporiasis was more likely to occur in foreign-born patients than in those born in the United States (adjusted odds ratio [OR] = 5.8, 95% confidence interval [CI] 3.4, 9.9, P < 0.001) and in Hispanics than in whites (non-Hispanics) (adjusted OR = 3.5, 95% CI 1.7, 7.2, P < 0.001). A prior history of PCP continued to be negatively associated with isosporiasis (adjusted OR = 0.2, 95% CI 0.1, 0.3, P < 0.001). Age and time remained independently associated with infection. These data suggest that isosporiasis among persons with AIDS in Los Angeles County may be related to travel exposure and/or recent immigration and that the use of trimethoprim-sulfamethoxazole (TMP-SMX) for PCP may effectively prevent primary infection or expression of latent isosporiasis. Physicians should have an increased index of suspicion for Isospora in AIDS patients with diarrhea who have immigrated from or traveled to Latin America, among Hispanics born in the United States, in young adults, and in those not receiving PCP prophylaxis. Food and water precautions should be advised and TMP-SMX prophylaxis considered for the prevention of Isospora infection for patients with human immunodeficiency virus infection who travel to Latin America and other developing countries.

Experimental transmission of Wuchereria bancrofti to monkeys.

Infective larvae of Wuchereria bancrofti from laboratory-raised Culex pipiens fatigans and Aedes togoi mosquitoes fed on human volunteers in Jakarta, Indonesia (J strain) and Kinmen Island, China (K strain) were introduced into Taiwan monkeys (Macaca cyclopis) by subcutaneous inoculation, by foot puncture, or by permitting infected mosquitoes to feed weekly on the monkeys. Some animals were splenectomized and others were treated with varying regimens of immunosuppressants. Necropsy was done on monkeys that died or were killed and the entire bodies were examined for worms. A total of 78 monkeys (43 males and 35 females) were exposed to infection and parasites were found in 29% of the females and 63% of males. In infections of 38 days or less worms were recovered from the testes of males and the pelt, carcass and lymph nodes of both sexes, but after 42 days of infection most worms were in the testes of males, and a few were recovered from lymph nodes and carcasses of females. Worms recovered at 8-11 days were third-stage, those found between 14 and 38 days fourth-stage, and ones found between 42 and 103 days were young adults. After 148 days most were adults and microfilariae were seen in the uteri of female worms at 160 days and later. The parasites continued to grow in size with time. Microfilariae were detected in the blood of nine monkeys between 8 and 18 months and the patent period varied from 5-21 months. Microfilarial densities were low and erratic, and periodicity could not be determined. The effectiveness of methods of administering infections and the value of various treatment regimens seem uncertain; monkey antilymphocytic sera, however, appeared to have some influence. Parasites were found in 36% of the Taiwan monkeys given the J strain and 54% of those given the K strain. A limited number of M. mulatta (3), M.irus (fascicularis) (3) and Aotus trivirgatus (4) were also given infective larvae and adult W. bancrofti were recovered from the testes of one male M. mulatta and one male M. irus; uterine microfilariae were found in one female worm from the latter monkey. A. trivirgatus were negative. Low numbers of infective larvae recovered from mosquitoes fed on patent monkeys were introduced intermittently into seven clean monkeys and one became microfilaremic between 11 and 17 months postinoculation.

Epidemiology of cryptosporidiosis among persons with acquired immunodeficiency syndrome in Los Angeles County.

To determine the occurrence and factors associated with Cryptosporidium among persons with acquired immunodeficiency syndrome (AIDS) in Los Angeles County, data were analyzed from the AIDS surveillance registry for the 10-year period 1983-1992. Among 16,953 persons with AIDS, a total of 638 (3.8%) cryptosporidiosis cases were reported during the study period. The prevalence of cryptosporidiosis was higher in persons whose suspected human immunodeficiency virus (HIV) exposure category was through sexual contact (3.9%) than among persons in other HIV exposure categories (2.6%; P < 0.01) and in immigrants from Mexico (5.2%) than in American born patients (3.8%; P < 0.01). Blacks (2.7%) were less likely than whites (4.1%) and Latinos (4.2%) to be reported with cryptosporidiosis (P < 0.001). A temporal trend was observed from 1983 to 1986 when the prevalence decreased from 6.7% to 3.6% (P < 0.001, by chi-square test for trend). After controlling for confounding variables by stratified analysis, persons whose HIV exposure was sexual (adjusted odds ratio [OR] = 1.7, 95% confidence interval [CI] 1.3, 2.4, P < 0.01) and immigrants from Mexico (adjusted OR = 1.6, 95% CI 1.2, 2.1, P < 0.01) were more likely to have cryptosporidiosis. The negative association with black race remained significant (adjusted OR = 0.7, 95% CI 0.57, 0.96, P = 0.02). The prevalence of cryptosporidiosis decreased with age in gay and bisexual males (Mantel-Haenszel test for trend, P < 0.01) but not among female and heterosexual male cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Balantidiasis in Aymara children from the northern Bolivian Altiplano.

Balantidium coli infection was coprologically studied in 2,124 Aymara children 5-19 years of age from the schools of 22 communities of the northern Bolivian Altiplano over a five-year period. Infection with B. coli was found in 11 of the communities surveyed, with prevalences of 1.0-5.3% (overall prevalence=1.2%). The prevalences observed are some of the highest reported and did not differ significantly among the various age groups or between boys and girls. These prevalences, the apparent absence of symptoms or signs of illness due to this parasite in the schoolchildren surveyed at the time of stool sampling, and the consistency of stool samples of the infected students suggest that they are apparently asymptomatic carriers. Infection with B. coli must be considered as an endemic anthropozoonosis in the area studied. A relationship between B. coli infection and Altiplanic pigs is suggested.

Microscopic diagnosis of blood parasites following a cytoconcentration technique.

An isotonic fixative (formalin and thimerosal) solution, with a saponin additive to lyse erythrocytes and platelets, has been developed. The formalin and thimerosal ensure good preservation of blood parasites. This fixative has led to the development of a new concentration technique using cytocentrifugation (cytospin) in the search for Plasmodium spp., Leishmania spp., and microfilariae, as well as leukocytes in which parasites or pigment may be present. The concentration of the parasites present in the sediment from 100 microl of blood spread on a 6-mm diameter circle results in good morphology that is well stained using the usual Giemsa or Wright techniques. This new technique has the advantage of a relatively low cost and offers the possibility of isolating and identifying in the same sediment the main blood-stage parasites, with the exception of young trophozoites, of Plasmodium falciparum.

Sensitivity and specificity of skin reactivity to Brugia malayi and Dirofilaria immitis antigens in Bancroftian and Malayan filariasis in the Philippines.

Saline antigen extracts of microfilariae, adult worms and third-stage larvae of subperiodic Brugia malayi maintained in gerbils were prepared for use as skin test reagents. Patients were studied on three different islands in the Philippines, one endemic for Bancroftian filariasis (Sorsogon, Luzon), another endemic for Malayan filariasis (Palawan) and the third without endemic filariasis (Cebu). A dose-response curve was established initially in patients with Bancroftian filariasis: thereafter 1.0 microng of the B. malayi antigens and 0.05 microng of Dirofilaria immitis FST antigen (obtained from Dr. T. Sawada) were used. Sizes of reactions were measured by recording the diameters of wheals at 20 minutes, 24 and 48 hours. There was a very high correlation in immediate hypersensitivity reactions among the three B. malayi antigens. Reaction sizes followed a normal distribution. When an area of an antigen-induced wheal 3 X that of the saline control was considered a positive reaction, 99% of 150 patients with Bancroftian filariasis and 96% of 45 subjects with Malayan filariasis reacted to B. malayi larval antigen. Only 68% of patients with Bancroftian filariasis but 90% of those with Malayan filariasis reacted to D. immitis FST antigen. There was no relationship between skin reactivity and age, sex, microfilaremia or severity of clinical disease. Approximately half of 50 patients who lived in an endemic area for W. bancrofti but had neither patent infection nor clinical disease reacted to B. malayi antigens. A maximum of 7% of 120 age- and sex-matched controls from Cebu gave false positive reactions with any of the antigens. Only a small proportion of patients gave 24- and 48-hour reactions. It is concluded that the use of antigens prepared from a human parasite, subperiodic B. malayi, which is easily maintained in a laboratory animal host, improves the ability to diagnose filarial infections by immunological means.

Analysis of Brugia pahangi microfilariae surface carbohydrates: comparison of the binding of a panel of fluoresceinated lectins to mature in vivo-derived and immature in utero-derived microfilariae.

A fluoresceinated lectin binding assay was employed to detect carbohydrates on the sheath and cuticle of mature in vivo-derived, and immature in utero-derived Brugia pahangi microfilariae. The sheath of mature microfilariae bound concanavalin A and wheat germ agglutinin, indicating the presence of N-acetylglucosamine and glucose or mannose. In addition to binding concanavalin A and wheat germ agglutinin, the sheath of in utero-derived microfilariae also bound Limulus polyphemus agglutinin, peanut agglutinin, Ricinus communis agglutinin-I, and soybean agglutinin, indicating the presence of the additional sugars galactose, sialic acid, and N-acetylgalactosamine. There was no evidence of cuticle carbohydrates, as none of the tested fluoresceinated lectins bound to either mature or immature exsheathed microfilariae. The significance of these results in terms of the survival of microfilariae in the mammalian host, and development to third-stage larvae in the mosquito vector, is discussed.

Susceptibility of various mosquitoes of California to subperiodic Brugia malayi.

Laboratory experiments were conducted to determine the susceptibility of six species of mosquitoes, representing three genera, to subperiodic Brugia malayi. The black-eye, Liverpool strain of Aedes aegypti was the susceptible control. Mosquitoes were fed on microfilaremic jirds (Meriones unguiculatus). All mosquitoes, except wild caught Culex erythrothorax, were laboratory-reared and allowed to feed when 8 to 10 days old. Anopheles freeborni, Anopheles hermsi, and Culiseta inornata proved refractory. Both Anopheles species allowed invasion of flight muscle and development to the late first stage, after which larval growth ceased and melanization occurred. Culiseta inornata prevented any larval development. Culex tarsalis and Cx. erythrothorax proved highly susceptible to B. malayi infection. In all, 95.6% and 88.7% of the Cx. tarsalis harbored third-stage larvae after infective feedings of 15.7 and 81.8 mf/microliters of blood, respectively, while only 11.5% were found susceptible when microfilaremia was low (1.1 mf/microliters). Culex erythrothorax demonstrated a susceptibility rate of 82.3% with 17.0 mf/microliters. Both Culex species appear to be excellent experimental hosts for subperiodic B. malayi. This is the first conclusive evidence that mosquitoes of the genus Culex can naturally support the complete development of a stain of subperiodic B. malayi.

Parameters influencing the susceptibility of neonate mice to infection with Brugia pahangi.

A total of 307 young mice between less than 1 day (neonate) and 4 wk after birth were inoculated either subcutaneously or intraperitoneally with infective larvae of Brugia pahangi to determine the best protocol for the establishment of patent infections. For both male and female neonates, i.p. infection produced higher adult worm burdens than did s.c. infection. Although the numbers of adult worms harbored by male and female mice were not statistically different, male mice were more prone to develop a patent infection; no neonate female mice became microfilaremic , whereas seven of 113 i.p.-infected male mice developed microfilaremia. More female adult worms were recovered, on the average, than were male worms, regardless of the age of mice used for infection. However, the younger the mice were at infection, the higher were the numbers of male worms recovered. A high number of gravid female worms were recovered from amicrofilaremic mice. Adult female and male worms harvested from amicrofilaremic mice, implanted into the peritoneal cavity of jirds (Meriones unguiculatus), did not produce microfilariae although approximately 50% of the jirds contained gravid female parasites. Jirds implanted with worms from microfilaremic mice did, however, contain peritoneal microfilariae. It appeared that amicrofilaremic mice irreversibly damaged female worms to the extent that worms could survive and appear healthy, but could not release microfilariae.

Characterization of the exposed carbohydrates on the sheath surface of in vitro-derived Brugia pahangi microfilariae by analysis of lectin binding.

Adult female Brugia pahangi were maintained metabolically active in vitro for up to 35 days in Click's medium supplemented with 10% horse serum. For the first 14 to 18 days microfilariae were released into culture. Although these in vitro-derived microfilariae were morphologically identical to in vivo-derived microfilariae, they could be differentiated by their characteristic of binding to a panel of fluorescein-conjugated lectins. The results suggest that maturation and release of microfilariae are correlated with glycosidic alterations on the sheath surface.

Increased susceptibility to infection with Brugia pahangi in aged female jirds (Meriones unguiculatus).

Female Mongolian jirds, Meriones unguiculatus, from 5 age groups of 2, 12, 16, 21, and 28 months, were infected with Brugia pahangi. Infections were followed for 125 days by weekly bleedings beginning 55 days postinoculation. Jirds were then killed and adult parasites recovered. Results showed a significant shortening of the prepatent period in the 12-, 21-, and 28-month-old groups. The proportion of gravid female worms did not vary significantly among the 5 groups. Similarly, the ratio of females to male worms showed little variation from group to group. Microfilaremia data for the 5 infection groups show an age-associated increase in numbers of circulating microfilariae. Some individuals in the 28-month group demonstrated 1,500 to 3,000 microfilariae per 0.25 ml peripheral blood, a level that was not approached by young females.

Karyotypes of Brugia pahangi and Brugia malayi (Nematoda: Filarioidea).

Using air-dried preparations of the testis and ovary, karyotypes were analyzed and compared to each other in two species of filarial parasites, Brugia pahangi and B. malayi. Both species had a diploid number of 10 chromosomes and were karyotypically very similar. C-banding analyses disclosed that the sex-determining mechanism of these species was of the XY-XX type, where the X chromosome was the largest, and the Y chromosome was of medium-size.

Ultrastructure of the rectum of infective-stage Wuchereria bancrofti (Nematoda: Filarioidea).

The authors have examined the ultrastructure of the rectum of infective-stage Wuchereria bancrofti by transmission electron microscopy. Our observations show that the rectum is divided into anterior and posterior segments. The cells of the anterior rectum appear to be derived from the microfilarial R (rectal) cells described by other authors. In both stages, these cells show voluminous nuclei, abundant mitochondria, and small cytoplasmic processes which contain fibrillar components. Amorphous material associated with these processes appears throughout the larval rectum and may protrude from the anus as the rectal plug. In the specimens examined, a patent lumen could not be traced completely through the anterior rectum. The posterior rectum has no counterpart in published accounts of microfilarial ultrastructure and probably arises during larval morphogenesis; it is lined with invaginated body cuticle, overlaid by a single layer of epithelial cells which may be of hypodermal origin.

The ultrastructure of adult Brugia malayi (Brug, 1927) (Nematoda: Filarioidea).

The ultrastruct of the adult subperiodic Brugia malayi (Brug, 1927) within pulmonary arteries of male jirds (Meriones unguiculatus) was studied by transmission electron microscopy. The cuticle consists of 10 sublayers (2 of which are prominently banded) and a typical outer unit membrane. Evidence is presented showing that the subcuticular region of the lateral chords comprises a functional complex of basal infoldings, multivesicular bodies, and associated mitochondria, which is probably engaged in the exchange of solutes across a permeable cuticle. Microbodies with paired, prominent cores, intracisternal A-particle viruslike bodies, nonstaining glycogen patches, and other structures are also present in the lateral chords. The platymyarian somatic musculature shares some coelomyarian characteristics, e.g., apparent neuromuscular connections and prominent glycogen deposits surrounded by mitochondria and other organelles. The alimentary tract has features typical of many nematodes. The luminal segments of the male and female reproductive tracts and their germinal products, excluding microfilariae, are described. Affinities with related species are discussed.

The lymphatic pathology of Brugia pahangi in the Mongolian jird.

We studied the sequence of histopathologic changes associated with Brugia pahangi (Nematoda: Filarioidea) infections in lymphatic vessels in the spermatic cord of the Mongolian jird (gerbil), Meriones unguiculatus. Intravascular granulomas caused mainly by disintegrating worms were seen in 67% of jirds necropsied on, or after, 35 days postinoculation, whereas none of 20 jirds examined before this day showed dying larvae. These granulomas usually evolved without vascular occlusion. Other granulomatous foci, often with a thrombuslike core, sometimes harbored microfilariae or microfilarialike materials. The perilymphatic cellular infiltrate consisted mostly of eosinophils, lymphocytes, and plasma cells. Large numbers of eosinophils were seen in the early weeks, but later declined, while lymphocytes increased to become the predominant cell in old infections. Irregular fibrosis of some valves and portions of the lymphatic walls were seen as early as the 2nd wk postinoculation. Lymphatic changes in the jird are similar to those described in other hosts infected with filariae, but remained moderate. Living worms appeared to be the stimulus for many observed changes. Most pathologic alterations were well established by 3 or 4 mo and showed little qualitative change during the remaining 4 mo of the study.

Ultrastructure of the anterior alimentary tract of infective-stage Wuchereria bancrofti (Nematoda: Filarioidea).

The anterior alimentary tract of infective-stage Wuchereria bancrofti is divided into the following segments: stoma or buccal capsule, muscular esophagus, glandular esophagus, esophageal-intestinal valve, and intestine. Invaginated external cuticle lines only the anterior stoma. External cuticle and esophageal lining are not continuous and are ultrastructurally distinct; the latter is compared morphologically to the amorphous component of elastin. The glandular esophagus is a composite structure of a stellate contractile epithelial core, surrounded by a sleeve of secretory epithelium. The glandular cytoplasm shows evidence of formation and release of dense secretory granules. At least 2 nerve cell bodies lie within the esophagus approximately 15 micrometer anterior to the esophageal-intestinal valve and their associated processes pass forward and backward through the contractile epithelium. Materials interpreted as ingested flight muscle mitochondria of the mosquito vector appear in various stages of degeneration within the intestinal lumen. It is suggested that, although simple by comparison to some other nematodes, the anterior alimentary tract of infective-stage W. bancrofti functions in the ingestion and breakdown of nutrient materials. The ultrastructure of the excretory cell likewise suggests a functional capability.