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The possible role of pigs as arbovirus maintenance hosts and their importance as amplifier hosts was studied. Blood samples from 464 pigs of all ages collected in 1962 and 1964 were tested against 10 arboviruses. Antibodies to Japanese encephalitis and Getah viruses were particularly prevalent and their calculated monthly infection rates were 19-5% and 13-3% respectively. In 1969, 447 pigs were bled monthly throughout the year and the infection rates for Japanese encephalitis virus were calculated in pigs during the first year of life. Infection rates were not uniform throughout the year; the rate increases as the pig grew older and there was a marked seasonal increase in the infection rate in the period from November to January. This coincided with the seasonal major population peak of Culex tritaeniorhynchus following intense breeding of this mosquito prior to rice planting. It is suggested that, in Sarawak, the pig acts as a maintenance host of Japanese encephalitis in a cycle involving C. gelidus mosquitoes and also acts as an important amplifier host towards the end of the year in a cycle involving C. tritaeniorhynchus. It is further suggested that Getah virus is maintained in a similar cycle between C. tritaeniorhynchus and pigs.

After an interval of four years the same observers used the same standardized techniques to re-examine 1,016 people in 12 heavily infected rain-forest and savanna villages in Cameroon. The changes in the number of nodules and in the concentration of microfilariae in the skin and eye are described. These latter changes are correlated with the development and/or deterioration of eye lesions and visual impairment. In both the rain-forest and the savanna there was a strong association between the development of eye lesions and a high concentration of microfilariae, not only in the eye but also in the skin, and more so at the shoulder than at the buttock. The importance of these findings for the prevention of blindness is discussed.

The antibody response to group C meningococcal polysaccharide vaccine was studied in a Nigerian village. Household clustering of poor responders to immunization was detected. Age had a marked effect on antibody response, maximal titres being obtained only in those over the age of 10 years. Children with malaria parasitaemia had a lower antibody response than those without parasitaemia and subjects with the genotype AA had a lower antibody response than those with the genotype AS. The antibody response to the vaccine was not influenced by mild degrees of malnutrition but children with clinical marasmus or kwashiorkor were excluded from the study.

In three double-blind placebo-controlled trials of pneumococcal capsular polysaccharide vaccines against death from acute lower-respiratory-tract infections (ALRI), children were vaccinated at 6 months to 5 years of age. The efficacy of the vaccines against ALRI as the sole cause of death was estimated at 59% in children vaccinated when younger than 5 years (p=0·008) and 50% in children vaccinated when younger than 2 years (p=0·043). Mortality from all causes was 19% less in the vaccinated group.

The control of the snail vectors of schistosomiasis by aerial application of the molluscicide N-trityl morpholine was carried out in a 80 000 ha area from 1974 to 1977. The effect of this molluscicide regimen on transmission of Schistosoma mansoni was monitored by longitudinal surveys in a number of schools and in pre-school-age children. A cross-sectional school survey was carried out in 1977.There was no significant difference in incidence between the treated area and an adjacent untreated area as measured by the longitudinal school survey, the longitudinal village survey, or the cross-sectional survey. Consideration of egg output and prevalence (as determined by ELISA test) also failed to reveal any difference between the two areas.The initial prevalence and intensity in the subjects selected from the treated area were higher than in the untreated area, and some villages showed possible transmission reduction. In general, however, the results showed a great variation in infection rates and intensity wi...

SUMMARYThis paper describes further characteristics of the immunization of sheep against schistosomes using live, irradiated schistosomula. Sheep immunized with a non-virulent strain of Schistosoma mattheei were protected against a more virulent strain of the same species for over a year. As there was no evidence that the irradiated parasites were able to persist this long, it was concluded that the vaccine had induced a sterile resistance. Heterologous vaccination, using irradiated S. mattheei schistosomula to immunize against S. bovis or irradiated S. mansoni schistosomula to immunize against S. mattheei, failed to induce any protection.

The results of an onchocerciasis survey of total populations aged 5 years and over in 16 heavily infected villages in Cameroon rain-forest and savanna zones are reported. Using standardized parasitological and clinical techniques the same observers examined the intensity of infection and clinical manifestations in 1,098 cases in the rain-forest and compared them with those found in 1,128 cases in the savanna. The following Table summarizes the main findings:- Rainforest Savana Prevalence of nodules 80–90% 60–70% Mean number of nodules per person +++ ++ Microfilarial skin density ++ −++ Skin atrophy ++ +++ Shin depigmentation +++ + Groin lymphadenopathy +++ ++ Hanging groin ++ + Microfilarial invasion of cornea ++ +++ Microfilarial invasion of anterior chmaber +++ +++ Microfilarial invasion of vitreous + ++ Snowflake corneal opacities ++ + Sclerosing keratitis + +++ Iritis + +++ Optic atrophy + + Choroidoretinitis + + Blindness 2.0% 5.1% + =at low level ++ =at medium level +++ at high level It is suggested that the differences between rain-forest and savanna may be due to variations in host response resulting from differences in the intensity and patterns of transmission. Different pathogenicity of the rain-forest and savanna strains of parasite is also considered to be of importance, and it is suggested that concomitant infections may influence the immunological response. Hormonal factors are considered to be important in influencing the differences in the patterns and severity of infections between males and females.

Cette etude confirme l'importance des bacteries dans l'etiologie et la pathogenie des infections aigues graves des voies respiratoires inferieures en Paponasie Nouvelle-Guinee. La bacteriemie quintuple presque le risque de deces. Homophilus influenzae et S. pneumoniae sont predominantes

The experiment described was conducted in water impounded by earth dams, for local water-supply, in Nyanza province, Kenya. Control of snails was attempted by introduction of the malacophagous fish Astatoreochromis alluaudi; other species were also introduced. The schedules of introduction of fish were varied between the reservoirs, and one was left as a control without any introduction of fish. The necessity for the establishment of a fish-rearing pond, prior to large-scale stocking, is emphasized.Assessment of snail control was made by scooping for snails, catches being expressed per man-hour. This was carried out both before and after introduction of fish, over a total period of 15 years. It is concluded that the data indicate that A. alluaudi did reduce the numbers of some species of snails—particularly Biomphalaria pfeifferi and, to a lesser extent and with less certainty, Bulinus spp.Two other introduced fish species, Tilapia zillii and T. leucosticta, did not appear to be associated with any fall in snail numbers.

A study of morbidity in Schistosoma mansoni infection was made in 593 Sudanese patients seen in a four-year period in Khartoum Civil Hospital. Clinical and laboratory findings were compared in three egg-count groups and in four clinical forms of the infection. Patients were divided into three levels of intensity of infection: light (up to 100 eggs/gram of stool), moderate (101--400 eggs/g) and heavy (more than 400 eggs/g). According to the presence or absence of visceral enlargement, infected subjects were divided into one of four clinical forms: intestinal, hepatic, hepatosplenic and splenic. Among the symptoms only the passage of blood in the stools was significantly related to intensity of infection, and fever was significantly related to the presence of hepatosplenic disease. Hepatomegaly and splenomegaly were significantly more frequent in the heavy infection group. Anaemia, eosinophilia, raised ESR and an increase in both serum alkaline phosphatase and serum globulins were significantly related to the intensity of infection. On the other hand, haematological and biochemical changes, as well as histopathological changes, were more marked and severe in patients with hepatosplenic disease. For comparison, the findings of 117 patients with S. haematobium infections and of 41 with dual S. mansoni/S. haematobium infections are included.

During a three-year period of effective control of Schistosoma haematobium transmission by molluscicide application the mean number of S. haematobium ova passed by subjects in the treated area fell in an exponential manner which suggested that the mean life span of the worm was 3·4 years. Parallel observations were made in a similar but untreated area. A comparison of the observations in these two areas suggested that in the untreated area subjects of all ages acquired infection during the course of the study. At the end of the study over 50% of the egg output in most age groups in the untreated area appeared to come from worms acquired during the preceding three years. There were substantial differences between age groups in the amount of infection acquired. Children, aged between eight and ten years at the end of the study, appeared to be passing perhaps a thousand times more ova from worms acquired during the preceding three years than were middle-aged subjects. Preliminary observations suggest that age- and sex-related differences in the pattern of water contact may not fully account for age- and sex-related differences in the rate of acquisition of infection and its prevalence. The probable significance of protective immunity in the epidemiology of schistosome infections is discussed.

Publisher Summary The subgenus Trypanozoon contains several kinds of trypanosome, which are morphologically indistinguishable but differ in their behavior. At various times specific or subspecific status has been accorded to each kind, but, in recent years, those cyclically transmitted by tsetse in Africa have been separated into subspecies of Trypanosoma brucei , while the others, transmitted non-cyclically outside the African tsetse belts, have retained separate species status. However, although such new terminology may be more correct taxonomically, the practical problems of distinguishing the trypanosomes remain. Enzyme electrophoresis is being used on an increasingly wide scale for the intrinsic characterization. However, as the number of enzyme systems being used for identification grows, comparison of stocks becomes increasingly difficult and intricate, particularly when an enzyme occurs in a multibanded form after electrophoresis. After using 12 enzyme systems to characterize 160 Trypanozoon stocks, the results have been analyzed to establish the degree of relatedness of each of the 59 zymodemest encountered. The detailed analysis is presented in this chapter.

A cross sectional study of schistosomiasis in migrant labourers in the Sudan Gezira is described. The people examined were of two ethnic groups: (i) those of local Arabic origin and (ii) those from Western Sudan, West Africa or west of longitude 27 °E. These two migrant groups were examined in one area treated with molluscicide and in another that was not. Almost all the schistosome infections were with Schistosoma mansoni , with a prevalence of 57% over-all and up to 89% in particular groups. The prevalence was lower in the treated than in the untreated area, and slightly lower in the Arab nomads than in the others, except that it was markedly lower in females from the West in the treated area. These results are consistent with the known water-contact habits of the two migrant groups. An association was observed between infection and liver and spleen enlargement, but not between infection and other symptoms. The potential importance of migrants in transmitting the infection is discussed.

After an interval of four years the same observers re-examined six rain-forest and six savanna villages, using the same standardized techniques. The results of these surveys have previously been reported by area, i.e. rain-forest and savanna. The present paper analyses the incidence of ocular changes by village. In the rain-forest the concentrations of microfilariae in the skin were similar in the six villages and there was, in general, little difference in the incidence and/or deterioration of ocular lesions between these villages. In the savanna the corresponding quantities were much higher in the three more heavily infected villages compared with the three less heavily infected ones. The implications of these findings for the control of blindness due to onchocerciasis in the savanna are discussed.

The results of an onchocerciasis survey of total populations aged 5 years and over in 22 village groups in Cameroon rain-forest and savanna are reported. Using standardized techniques the same observers examined skin and eye lesions in 2,678 persons infected with O. volvulus , and compared them with lesions in 1,156 persons in whom the parasite was not detected.

The intensity and prevalence of proteinuria and haematuria were studied with urinanalysis reagent strips in a Gambian community in which the intensity of infection with Schistosoma haematobium was high. The level of proteinuria present was shown to be related to the intensity of infection. Follow-up for 12 months showed that infected subjects with heavy proteinuria had a good prognosis. These findings suggest that the urinary protein in such subjects is likely to originate from lesions in the bladder and ureters and that advanced glomerular pathology is probably rare. The relationship of the levels of proteinuria and haematuria to the egg count suggests they may be parameters which could have value as indications for chemotherapy. Detailed study showed that the effect of treating all the subjects who had both 30 mg/100 ml or more of protein and at least a trace of haematuria would have been very similar to treating all those with an egg count of 200 ova/10 ml or more. Since urinanalysis with reagent strips is very simple and rapid it could have a role in mass chemotherapy campaigns, particularly those aimed at the identification and treatment of heavily infected subjects.