Consequences of protein supplementation for anorexia, expression of immunity and plasma leptin concentrations in parasitized ewes of two breeds.

The periparturient relaxation of immunity (PPRI) against parasites in ewes has a nutritional basis. We investigated whether ewes experience a reduction in food intake (anorexia) during PPRI and if the magnitude of anorexia is affected by host production potential and dietary protein supplementation. We also investigated whether nematode infection is linked to plasma leptin concentrations in periparturient ewes. The experiment was a 2 x 2 x 2 factorial design. Two breeds of twin-bearing/lactating ewes (Greyface cross, G (n 32) and Scottish Blackface, B (n 32)) were used. Half of the ewes were trickle infected with 30,000 larvae of the abomasal parasite Teladorsagia circumcincta per week and the other half were not. During the experiment, all ewes had ad libitum access to a low-protein diet that provided less protein than the recommended allowance. In addition, half of the ewes received a protein supplement that resulted in protein intakes that exceeded recommendations. Nematode infection resulted in a breakdown of immunity to parasites and a reduction in food intake in both breeds. The breeds differed in the extent of PPRI (G ewes having higher faecal egg counts than B ewes), but not in the magnitude of anorexia. Protein supplementation resulted in a reduction in faecal egg counts, but had no effect on the magnitude of anorexia. Plasma leptin concentrations changed significantly over time, but were not affected by protein supplementation or infection. It is concluded that infection with T. circumcincta in periparturient ewes results in anorexia that is not alleviated by protein supplementation and seems unrelated to plasma leptin concentrations.

Nutritional impact of intestinal helminthiasis during the human life cycle.

Poor people in developing countries endure the burden of disease caused by four common species of soil-transmitted nematode that inhabit the gastrointestinal tract. Disease accompanying these infections is manifested mainly as nutritional disturbance, with the differing infections having their deleterious effects at different phases during the human life cycle. Reduced food intake, impaired digestion, malabsorption, and poor growth rate are frequently observed in children suffering from ascariasis and trichuriasis. Poor iron status and iron deficiency anemia are the hallmarks of hookworm disease. The course and outcome of pregnancy, growth, and development during childhood and the extent of worker productivity are diminished during hookworm disease. Less is known about the impact of these infections in children under 2 years of age. The severity of disease caused by soil-transmitted nematodes has consistently been found to depend on the number of worms present per person. Cost-effective measures based on highly efficacious anthelminthic drugs are now available to reduce and control disease caused by these infections.

Soil-transmitted nematode infections and mebendazole treatment in Mafia Island schoolchildren.

In August 2000, a cross-sectional study was performed to assess the prevalence and intensity of soil-transmitted nematode infections in schoolchildren on Mafia Island. Hookworm infection was widespread (72.5% prevalence) whereas Trichuris trichiura was less prevalent (39.7%) and Ascaris lumbricoides was present at a low prevalence (4.2%), mainly in urban areas. In a subsample of the study population, both Necator americanus and Ancylostoma duodenale were found, although N. americanus was more prevalent. This survey was followed by a parasitological evaluation of mebendazole treatment using a single, 500-mg dose. The data on outcome were used for comparison with those from recent studies of similar treatment regimens in the neighbouring island of Pemba, Zanzibar, where periodic chemotherapy with mebendazole to schoolchildren has been implemented as part of a helminth-control programme since 1994. A higher efficacy of mebendazole against hookworm infection was found in Mafia Island (where a cure 'rate' of 31.3% and an egg-reduction 'rate' of 78.1% were recorded) when compared with that observed in Pemba Island, possibly indicating that hookworms may be developing mebendazole resistance on Pemba Island as a result of intense exposure to the drug there.

Sociocultural factors in the control and prevention of parasitic diseases.

Control and prevention of parasitic disease depends on an adequate knowledge of interactions among factors such as human behavior, the environment, and the life cycles of parasites. Sociocultural factors in large part determine transmission and persistence of parasites. The main determinants are poverty, low educational level, deficiencies in home technologies, high demographic density, and ruralism. Selected interventions designed to improve any of these situations may fail if they are applied in an isolated manner. The holistic implementation of interventions has proved successful in the control and prevention of parasitic infections in several parts of the word. The implementation of several kinds of interventions simultaneously, that is, a holistic approach, combined with an awareness of a society's infrastructure, can produce favorable results. For such an awareness--when it provokes action--can improve the overall quality of life.

Hookworm disease: host-pathogen biology.

The hallmark of hookworm infection, a common helminthic disease, is iron deficiency anemia. The development of anemia is dependent on the intensity of infection, the species of hookworm, and the ability of the host to resist infection and to maintain adequate stores of iron. When conditions are appropriate, the incidence of anemia caused by hookworm is high and has a significant economic impact since it results in a reduction of worker productivity. Loss of blood is caused by direct ingestion of red cells and by tissue trauma produced by worm attachment and feeding. This focal trauma may involve multiple villi and is characterized by local hemorrhage, tissue cytolysis, and neutrophilic response. Although focal intestinal lesions are apparent, their significance is questionable since diffuse mucosal changes are absent in intestinal biopsies of patients with heavy hookworm infection. Short-range control measures protecting against hookworm infection have not succeeded. Development of a vaccine against hookworm infection in humans is problematic since functional protective immunity in humans has not yet been demonstrated and no suitable animal model of hookworm infection in humans is available. At present, the most effective method of intervention appears to be supplementation of food staples with iron.

Anthelmintic control of concurrent Hymenolepis nana and Syphacia obvelata infections in the mouse with uredofos.

Tests were made to determine the efficacy of uredofos in either the diet or drinking water for controlling induced Hymenolepis nana and naturally acquired Syphacia obvelata infections in the mouse. Four levels of administration (50, 75, 100, and 125 parts per million) were used in a 6-day drugdiet assay. Consistent removal of Hymenolepis nana occurred only at 125 parts per million, whereas removal Syphacia obvelata was complete at all levels. The disodium salt of uredofos was given in the drinking water. Three levels of administration (12, 18 and 25 mg/kg) were used, and the treatment period was limited to 24 hours. Complete removal of Hymenolepis nana occurred at 25 mg/kg and Syphacia obvelata was completely eliminated at all levels.