Field evaluation of two diagnostic antigen tests for Wuchereria bancrofti infection among Indian expatriates in Saudi Arabia.

Two commercially available diagnostic tools (Tro-Bio ELISA and ICT card test) were used to detect circulating filarial antigen of Wuchereria bancrofti infections among Indian expatriate workers in Saudi Arabia. Daytime serum samples collected from 302 individuals (210 men and 92 women) were tested. Night blood surveys for microfilaraemia were restricted to those individuals who became positive for the trop-Bio assay test. The overall prevalence of filarial antigeaemia was 10.6% (32 individuals). Of these 32 antigen positive cases, microfilariae were found in 10 men (31.3%), with a mean microfilarial count of 105 mff/ml. No positive antigen results were found in control sera from 200 native healthy Saudis or from patients with helminthic infections (schistosomiasis, echinicoccosis, hookworm, ascariasis and trichuriasis). All 32 positive sera with the Trop-Bio ELISA showed a positive ICT card reaction (specificity and sensitivity 100%). It is concluded that, in Saudi Arabia and other Gulf states, where a continuous flow of south- and southeastern workers coming from areas endemic for bancroftian filariasis, the ICT card test may be useful in monitoring the potential risk of introducing bacncroftian filariasis to the host countries.

The validity of the Reflotron as a screening tool for blood cholesterol.

Screening for blood cholesterol levels has become an essential need in many countries. The aim of this study was to evaluate the performance of Reflotron analyzer in screening for blood cholesterol in terms of its precision and accuracy. We have compared the results obtained by the Reflotron with those obtained by a standard hospital laboratory procedure for the same samples. An optimal precision that met the 1992 LSP standards for precision was observed (CV = 2.27%). On the other hand, a suboptimal accuracy of Reflotron was detected, where more than 80% of the Reflotron values differed from the reference laboratory values by more than 5%. As a consequence, 21% of individuals were misclassified as normal due to the very low sensitivity in spite of the optimum specificity observed for the Reflotron. Using the receiver operating characteristic curve analysis, the optimum cut-off points giving the best validity values for the test were 170 mg/dl and 190 mg/dl (4.4 mmol/L and 4.9 mmol/L) for the border-line and true hypercholesterolemia, respectively. At these levels, sensitivity was 0.89 and 0.86, specificity 0.93 and 0.93, and positive predictive value was 0.91 and 0.82, respectively. Considering some limitations of the study, it is concluded that the Reflotron could be of more potential validity for the use in cholesterol measurement surveys when the recommended cut-off points are used.

Skin diseases among adolescent boys in Abha, Saudi Arabia.

BACKGROUND: Adolescence is characterized by a sensitivity to issues of attractiveness. With dermatologic conditions, this may adversely affect early detection and compliance. METHODS: A cross-sectional study was carried out on a multistage stratified random sample of 647 adolescent schoolboys in Abha, Saudi Arabia, to determine the prevalence of skin diseases. The age of the boys ranged from 11 to 19 years with an average of 15.3 +/- 1.9 years. RESULTS: It was found that 19.8% of the children were affected by one form or another of transmissible skin diseases (TSD). The most common types were: pediculosis capitis (9.6%), verruca vulgaris (3.9%), and tinea pedis (1.9%). The prevalence of TSD increased significantly as the age decreased and as the crowding index increased. As for non-transmissible skin diseases, acne vulgaris was the most prevalent disease (56.3%). The prevalence and severity of acne increased significantly as the age increased. CONCLUSIONS: The findings indicate the need to develop regional intervention programs at the school level. Appropriate continuing medical education programs for school health workers in the region are mandatory to achieve this goal.

Onchocerca fasciata: enzyme histochemistry and tissue distribution of various dehydrogenases in the adult female worm.

Histochemistry studies of key dehydrogenases in the glycolytic pathway and related enzymes and the tricarboxylic acid (TCA)-cycle enzymes were carried out on adult female Onchocerca fasciata. The distribution pattern and enzymatic activities of 6-phosphogluconate dehydrogenase (6-GPDH), lactate dehydrogenase (LDH), mitochondrial glycerol-3-phosphate dehydrogenase (GPDH), nicotinamide adenine dinucleotide (phosphate) [NAD+(P)]-linked isocitrate dehydrogenase (ICDH), and NAD+(P)-linked malate dehydrogenase (MDH) in various tissues of the worm were determined. Moderate to intense enzyme activities were localized in three main areas, namely, the hypodermis, body-wall muscle, and reproductive tissues. Activity of the formazan reaction product was very low, if at all present, in the intestinal epithelium and was completely absent in the cuticle. On the basis of the present results and earlier observations, it is suggested that glycolysis leading to the end product lactate is the main energy-generating pathway in O. fasciata. The presence of significant activity of 6-GPDH indicates that the pentose-phosphate pathway might be operative in O. fasciata. In light of the activity of some of the TCA-cycle enzymes, ICDH and MDH, demonstrable in O. fasciata, it is possible that an additional pathway (pyruvate-succinate) of glucose metabolism via a reverse sequence of the TCA cycle may also be operative in the worm. The possible functional significance of the enzymes detected is discussed with respect to their location.

Impact of chlorination of water in domestic storage tanks on childhood diarrhoea: a community trial in the rural areas of Saudi Arabia.

During the period September 1991 to February 1992 standard chlorination packages of calcium hypochloride were provided for the first time to 171 families residing in the catchment area of the Sabt-Bany Bishr Primary Health Care Centre in the rural areas of the Asir region, south-western Saudi Arabia. The villagers added the packages to their home storage water tanks each time they added water from the 220 nearby wells. Analysis of the water samples taken from these wells showed that all of them were bacteriologically unfit for human use. By the end of the study period there were no bacteriologically unfit water samples taken from the tanks of the participating families. Children under 5 years of age whose families were not using chlorinated water had twice the risk of diarrhoea compared to children from the participating families (odds ratio = 1.98, P = 0.047). The use of chlorinated water was associated with a 48% reduction in diarrhoea. These results indicate that the chlorination of water can be successfully carried out locally in rural areas to improve the health of the population.

Parasitic infections and gastrointestinal symptoms among preschool children in day care centers in Alexandria, Egypt.

There is a considerable amount of speculations concerning the presence of symptoms in various parasitic infections. The aim of the present study was to determine the prevalence of different parasitic infections among children in day care centers (DCCs), and to establish the relation of such infections to gastrointestinal symptoms. A total of 623 stool samples were collected from 700 preschool children aged 2-5 years who attended 3 DCCs of different social classes in Alexandria. These samples were tested for parasitic infection by the conventional microscopy. Parents were interviewed as regards the gastrointestinal symptoms frequently suffered from by their children included in the sample during the 3 months period preceding the interview. The prevalence rate of parasitic infection was 56.0%. Giardiasis was the commonest infection (34.7%), followed by Ascariasis (24.4%) and Trichuriasis (4.6%). Boys showed a significantly higher prevalence than girls (58.3% vs. 52.9%, p<0.01). Social children were more infected with G. lamblia than unsocial ones (39.6% vs. 22.1%, p<0.01). Vomiting was strongly associated with G. lamblia infection (OR=7.1, p<0.01), diarrhea with multiple infections (OR=48.2, p<0.01), while abdominal pain was not significantly associated with any of these infections. The high prevalence of Giardiasis in DCCs emphasizes the need for increased surveillance for G. lamblia as a cause of vomiting in children, especially among active and social boys. Routine and periodic administration of a protozoan treatment to such children is recommended.

Prevalence of antibodies to Toxoplasma gondii among blood donors in Abha, Asir Region, south-western Saudi Arabia.

One thousand samples of sera from healthy blood donors in the Asir Central Hospital, a tertiary facility in the Southwestern part of Saudi Arabia, were screened for Toxoplasma gondii IgG antibodies by the Indirect Haemagglutination Antibody (IHA) test. A prevalence of 52.1% was found. Seropositivity increased with age. The Geometric Mean Titre (GMT) of IHA antibodies was 596.7. While the prevalence increased with age, the GMT declined in the higher age groups. Three hundred sixty six of these sera were also tested for specific IgM titres by micro ELISA technique and 4.1% were found positive, indicating possible acute or recent infection. These serological studies indicate a higher prevalence of toxoplasmosis among healthy blood donors in the Asir region compared to earlier seroprevalence studies in other areas of Saudi Arabia. The high frequency in antibody titres might be due to differences in climatic conditions, culinary habits and exposure to the sources of infection. In view of these findings, it is felt that when considering blood transfusion for a special group of patients (i.e. immunocompromised or immunosuppressed), it would be wise to exclude those with evidence of previous exposure to T. gondii.

Acceptability and usage of permethrin-impregnated mosquito bed nets in rural southwestern Saudi Arabia.

In 1989 a total of 2,320 sets of locally-made durable permethrin-impregnated bed nets and support frames were provided for the first time to 410 families (2,485 individuals) in Al-Fateeha area in the malarious region of Tihamat Asir, southwestern Saudi Arabia. In interviews carried out with a sample of the heads of the families two years later, most of them said to have used bed nets regularly (78.3%) and a majority started using them shortly after sunset (73.9%). Most heads of families expressed willingness to encourage their friends and neighbours to get bed nets (94.4%) and use them regularly (92.9%). Public requests for bed nets were received from neighbouring areas. These results indicate that impregnated bed nets can be successfully integrated into a malaria control programme provided that they are of a durable type and accompanied with support devices to facilitate their use while sleeping outdoors. Records of the primary health care centre serving the trial area indicated that the incidence of malaria decreased progressively from 277.4 per thousand in 1988 to 124.4 in 1991. The possible contribution of mosquito nets--as a major newly introduced variable--to this decrease is suggested but was not directly measured.

Histochemical distribution of esterases in adult Onchocerca fasciata (Filarioidea: Onchocercidae).

The localization and distribution patterns of non-specific esterases (NSE) and acetylcholinesterase (AChE) activities in adult female Onchocerca fasciata (Filarioidea: Onchocercidae) have been determined using enzyme histochemical techniques. NSE activity was highest in the hypodermis and mild to moderate in the somatic musculature and uterine epithelium. The intensity of the reaction was decreased but not eliminated by sodium fluoride. AChE activity was found in the hypodermis and cuticle of the female worm, highest in fully formed microfilariae in the uterus, whereas early oocytes and embryonic forms were negative. Butyrylcholinesterase activity showed similar but less intense staining reactions at the same sites. Eserine-treated sections showed no AChE activity in all areas where it is usually present. The present techniques failed to demonstrate AChE activity in the nervous tissue including the hypodermal nerve trunks and neuromuscular junctions of the worm. The possible functional significance of the demonstrable enzymes was discussed with respect to their location. NSE activity may be involved in lipid metabolism, whereas AChE activity may have a role in host-parasite relationship.

Falciparum malaria in naturally infected human patients: II. Ultrastructural alterations to erythrocytes infected with asexual forms.

Ultrastructural alterations of human erythrocytes infected with asexual forms of Plasmodium falciparum were studied in naturally infected Saudi patients. These included surface knobs and nodules as well as invaginations associated with cytoplasmic vesicles observed in erythrocytes infected with asexual forms of the parasites. Such nodules and surface invaginations have been previously described only in erythrocytes infected with P. ovale and P. vivax, respectively. Within the cytoplasm of infected erythrocytes were membrane-bound clefts, similar to those that appear to be a common characteristic in all red cells infected with malaria parasites. Vacuolations were often seen in the peripheral cytoplasm and may represent hemolyzed areas. Collapsed cells with an internal-lucent interior and surrounded by an irregularly folded membrane may represent completely hemolyzed erythrocytes.

Falciparum malaria in naturally infected human patients: I. Ultrastructural differences between malaria pigments in intraerythrocytic asexual and sexual forms.

Venous blood samples were taken from patients naturally infected with the human malaria parasite Plasmodium falciparum. Two types of malaria pigment (MP) particles have been demonstrated in intraerythrocytic asexual forms (trophozoites and schizonts), while a single type was detected in gametocytes. Type I MP particles, found in both asexual and sexual forms, are electron-dense. It is suggested that these are proteinaceous and may be intermediate, utilizable metabolic products that serve as a food reserve during development of the parasite in the human host and also during the growth cycle of the sexual form in the mosquito. In asexual forms, type I particles occur within food vacuoles (FV) containing semidigested hemoglobin (Hg), while they are unenveloped in the cytoplasm of the sexual forms. Type II MP particles, found in electron-lucent residual bodies, are crystalloid and of low electron density. It is suggested that these are the final, waste product of Hg digestion in the asexual forms.

Gamma delta T cells and the immune response in visceral leishmaniasis.

Visceral leishmaniasis (VL) caused by Leishmania donovani, a protozoan parasite, is a disease of high morbidity associated with hepatosplenomegaly, hypergammaglobulinemia, fever and death. One of the immunological hallmarks of VL is a remarkable increase in serum immunoglobulin levels as a result of polyclonal B cell activation. This study demonstrated that T lymphocytes expressing the T cell receptors (TcR) gamma delta in association with CD3 molecules are increased in circulation of patients with VL. A large proportions of TcR gamma delta-bearing T cells had CD4+ CD8- phenotype, and expressed CD25, CD38, CD71 and HLA-DR activation antigens. Furthermore, we demonstrated wide functional differences in TcR gamma delta and TcR alpha beta T cells in their proliferative response, secretion of interleukin-2 (IL-2), B cell growth factor (BCGF) and B cell differentiation factor (BCDF). It was of interest that the TcR gamma delta T cells from patients with VL could be expanded by in vitro culture with human recombinant IL-2. Although these TcR gamma delta T cells secreted diminished levels of IL-2, they produced highly augmented levels of both BCGF and BCDF, suggesting that secretion of these lymphokines in these T cell subsets is regulated independently. The relative increases in the CD4+ CDw29+ TcR gamma delta T cell subsets and their secretion of highly elevated levels of BCGF and BCDF largely accounted for the humoral immune system abnormality and hypergammaglobulinemia found in this disease. These observations may help to explain that TcR gamma delta T cells might be functional in vivo and are involved in immunological mechanisms of pathogenesis in VL.