Epidemiology and transmission of rotavirus infections and diarrhoea in St. Lucia, West Indies.

To determine the epidemiology and risk factors of rotavirus infections in St. Lucia, 229 children in three valleys with varying levels of sanitation were studied for 2 years. A four-fold rise in complement fixation antibody to rotavirus antigen was used in paired samples as evidence of recent infection. Results showed that forty-eight per cent of infants experienced at least one infection during a two-year period, and 17% of children were reinfected. Infections occurred within the first months of life and peaked between 6 and 23 months of age. The peak infection coincided with the dry season in each age group. Children breast-feeding had fewer infections. Although crowding within the home was significantly associated with repeated infection, the incidence of infection was not affected by the degree of sanitation. Other studies in the region, using recently developed techniques, concur with these findings which advance our understanding of the epidemiological importance of rotavirus in St. Lucia. Although these studies provide insights into the risk factors for rotavirus infections, other studies are required to determine whether investments should be focused on improved sanitation or immunization or both.

PIP: During the 1977-1979 Schistosomiasis control project in St. Lucia, researchers studied the prevalence of rotavirus infection in 229 children 3 years old (10 children later dropped out of the study) in 3 valleys with different levels of sanitation. Nurses from the Ministry of Health collected stool and sera samples which laboratory staff tested for rotavirus and antibodies, 48% (106) had at least 1 rotavirus infection during the 2 years. 18 of them were reinfected once and 1 twice. Prevalence was highest in 1 year olds (18.1% 12-176 months; 18.9% 18-23 months). Rotavirus caused diarrhea in 47% of all diarrhea cases during the dry season (April-June), but only 3% during the rainy season (October-December). Only children 6-23 months old had significantly higher infection rates during the dry season. Breast fed children 0-11 months had a lower infection rate than those bottle fed or other wise fed. Crowding was the only consistent and significant social factor associated with rotavirus infection (p.05). Rotavirus infection prevalence remained similar for the 3 different hygienic areas which demonstrated that improved sanitation only affected diarrhea not caused by rotavirus. The fact that children with rotavirus reinfections lived in crowded dwellings and that crowding was significantly associated with rotavirus infections suggested that air may have been responsible for transmitting rotavirus. Other studies are needed to see whether efforts to reduce diarrheal morbidity should center on improved sanitation or immunizations or both.

Epidemiology and transmission of rotavirus infections and diarrhoea in St. Lucia, West Indies

To determine the epidemiology and risk factors of rotavirus in St. Lucia, 229 children in three valleys with varying levels of sanitation were studied for 2 years. A four-fold rise in complement fixation antibody to rotavirus antigen was used in paired samples as evidence of recent infection. Results showed that forty-eight per cent of infants experienced at least one infection during a two-year period, and 17%of children were reinfected. Infections occured within the first months of life and peaked between 6 and 23 months of age. The peak infection coincided with the dry season in each age group. Children breast-feeding had fewer infections. Although crowding within the home was significantly associated with repeated infection, the incidence of infection was not affected by the degree of sanitation. Other studies in the region, using recently developed techniques, concur with these findings which advance our understanding of the epidemiological importance of rotavirus in St. Lucia. Although these studies provide insights into the risk factors for rotavirus infections, other studies are required to determine whether investments should be focused on improved sanitation or immunization or both

Larvicidal activity of albendazole against Necator americanus in human volunteers.

This study evaluated the efficacy and tolerance of a single oral 400-mg dose of albendazole on Necator americanus larvae, and compared its efficacy when administered between meals or with a meal. Twenty-nine healthy and hookworm-free male volunteers were exposed on the forearm to approximately 45 8-day-old N. americanus larvae. All subjects developed discrete maculopapular eruptions at the site of larval application. Following a random double-blind study design, each subject received at the end of the 6th post-infection day either the investigational drug or a placebo as follows: Group I (n = 8)-placebo; Group II (n = 11)-400 mg albendazole with a meal; Group III (n = 10)-400 mg albendazole 3 or more hours after or before a meal. On day 56 post-infection, the stools of all subjects who received placebo were positive for N. americanus eggs (by zinc sulfate flotation technique), compared with 48% positivity (10/21) in those who received albendazole (P = 0.01). By day 63 post-infection, an additional three subjects in the treatment group became positive, for an overall 62% rate of positivity (13/21), i.e., albendazole prevented patent infection in 38%. Administration of albendazole with a meal did not alter drug efficacy. In those subjects in whom patent infections were not prevented, egg output was one-fourth that of the placebo group. There was no difference in viability of eggs appearing in feces of treated and untreated subjects as judged by larval development in Harada-Mori cultures. Our data indicate that albendazole is active against pre-intestinal stages of N. americanus in human infections.

Routine focal mollusciciding after chemotherapy to control Schistosoma mansoni in Cul de Sac valley, Saint Lucia.

Concluding results of a 10-year schistosomiasis control programme in Cul de Sac valley, Saint Lucia, are described. After an area-wide mollusciciding campaign (1970-75), and a surveillance/treatment programme supplemented with selective population chemotherapy in 1975 and 1976, prevalence rates of Schistosoma mansoni were reduced to low levels. To prevent a resurgence of transmission a cost effective routine focal mollusciciding programme, suitable for public health implementation was evaluated from 1977 to 1981. Streams and main collector drains in banana fields, considered to be potential S. mansoni transmission sites, were treated every four weeks with Bayluscide 6076 emulsifiable concentrate (Clonitralide). Snail populations were effectively controlled in the treated areas but large numbers were present where no treatment was given. Only 0 X 06% of sentinel snails became infected. Prevalence of infection in the human population remained low (over-all 5%) and intensity of infection at a level not normally associated with schistosomal disease. Since control started 10 years earlier the level of potential contamination has fallen by 92% in high transmission areas. The four-year programme cost US+12,909 of which 54% was for molluscicide, 27% for labour and 19% for transport, equipment and sundries. The average annual cost per head of population was US+0 X 46.

Value of individual household water supplies in the maintenance phase of a schistosomiasis control programme in Saint-Lucia, after chemotherapy.

Between 1970 and 1975, the incidence of new Schistosoma mansoni infections was reduced in 5 villages after each household was provided with its individual water supply and community laundry shower units were made available. In 1975, 1976, and 1977 chemotherapy with oxamniquine was offered to persons found to be infected. Transmission was reduced further and remained at a low level for the next 4 years, with no sign of an increase in spite of the reservoir of infection remaining after therapy and a poor level of sanitation in the villages.Thus, properly maintained water supplies appear to be effective in maintaining transmission at a low level during the maintenance phase of a schistosomiasis control programme, after chemotherapy. Sporadic new infections must be anticipated among children, but these will probably be of low intensity and associated with minimal morbidity.

Evaluation of chemotherapy in the control of Schistosoma mansoni in Marquis Valley, Saint Lucia. I. Results in humans.

Hycanthone at a dose of 2.5 mg kg body weight was given in 1973 and 1974 to persons found by a sedimentation concentration technique to be excreting Schistosoma mansoni eggs. In a further two campaigns oxamniquine was used (15 mg/kg body weight). The last treatment was given after the 1976 survey and stools of children were re-examined annually but not further treatment was planned. In six villages prevalence remained low, at 4%, 4 years later, in two it increased to 10%, and in two others after 3 years it was 23% and further treatment was offered. Factors affecting renewed transmission and the rate prevalence builds up were investigated and found to be low attendance rate for treatment, greater use of the river water and, possibly, infected immigrants. But if prevalence builds up slowly, retreatment may be necessary only every 3-4 years at an estimated annual cost of 40 cents per person protected.

Reduction in transmission of Schistosoma mansoni by a four-year focal mollusciciding programme against Biomphalaria glabrata in Saint Lucia.

The effect of transmission of Schistosoma mansoni of a focal snail control programme was investigated over four years amongst approximately 1250 people living in five communities in the steep-sided Soufriere river valley, St. Lucia, West Indies. Bayer 6076 was applied from constant flow drip cans to 12 stream sections at a target dose of 8 mg/litre clonitralide every four weeks. Only proven and potential transmission sites were treated; marsh habitats, where Biomphalaria glabrata were widespread, were ignored. In the stream snail numbers were reduced by 94% in the first year and by 100% thereafter. Incidence of new S. mansoni infections amongst children fell from 18% in the last year before control to 6% and 9% after three and four years respectively. Amongst children and adults in the four years of control the conversion/reversion ratio declined leading to a lowering of the over-all prevalence from 40% to 22%. Parasitologically the results were similar to those of a previously evaluated area-wide mollusciciding programme. The mean annual cost per person protected was US $2.60. This figure is atypically high because the topography of the area severely limited the population size.

Comparison of ELISA, radioimmunoassay and stool examination for Schistosoma mansoni infection.

A comparison was made of the sensitivity and specificity of four diagnostic tests for Schistosoma mansoni infection in a community of 516 untreated persons in St. Lucia, West Indies. Prevalence of infection as obtained by: (i) the Bell filtration technique was 44.4% (one filter) and 63.2% (three filters); (ii) the Kato thick smear, 60.2%; (iii) by radioimmunoassay (RIA), 73.3%; and (iv) enzyme-immunoassay (ELISA) 70.9%. The age distribution of persons serologically positive but parasitologically negative showed these to be mostly children and persons 40 years old and over. By means of a statistical test due to Cochrane, it was concluded that there was no evidence to indicate a difference between paired serological tests and paired parasitological tests in their diagnostic capability. There was a very significant difference between the Bell technique and the other three tests. The ELISA emerged as a less satisfactory test than the RIA or the Kato thick smear. The levels of sensitivity and specificity of each test were measured by Armitage's "J" index. The reliability of the Bell filtration technique was 64%, of the ELISA 68%, of the RIA 78% and of the Kato 85%.

Schistosoma mansoni control in Cul de Sac Valley, Saint Lucia. II. Chemotherapy as a supplement to a focal mollusciciding programme.

After an intensive area-wide mollusciciding campaign, over four and a half years, transmission of Schistosoma mansoni was reduced. A cheaper scheme suitable for the follow-up or consolidation stage of control was evaluated and two selective population chemotherapy campaigns using hycanthone (2 mg/kg b.w.) and oxamniquine (15 mg/kg b.w.) were mounted. Prevalence dropped to 6% and 3% in areas with previously high and low levels of transmission respectively. Calculations suggested that these figures were falsely low and that perhaps 20% of the population were still excreting S. mansoni ova in small numbers. The unco-operative groups in the population are probably more important in maintaining a reservoir of infection in the community than persons with light infections undetected by the sedimentation concentration stool examination technique used. The benefit of more sensitive but more costly examination techniques is not clear since the importance of very light infections in transmission is uncertain. Case detection absorbs an increasing proportion of the total cost of chemotherapy programmes with fewer cases being found amongst the same number screened. Using hycanthone (649 treated) the cost per person protected was $0.74 and using oxamniquine (264 treated) $0.94. The need to develop low cost consolidation or follow-up procedures for preventing a resurgence of transmission after successful control, when the infection is no longer of public health importance, is stressed.

Lack of association of hepatosplenic schistosomiasis and alpha-1-antitrypsin deficiency.

To evaluate the role of alpha-1-antitrypsin deficiency in the pathogenesis of hepatosplenic schistosomiasis, alpha-1-antitrypsin was measured in 90 patients with schistosomal splenomegaly and in 87 phenotyping was also done. All levels were in the normal range except for those of two patients who were shown to have the heterozygous deficiency state, PiMZ. The phenotypes found in the 87 were as would be expected in a normal population. Alpha-1-antitrypsin deficiency does not play a significant role in the pathogenesis of hepatosplenic schistosomiasis.

Quality control in laboratory investigations on Schistosoma mansoni in St. Lucia, West Indies. Maintenance of artificial prevalence as a laboratory aid.

A method is described of maintaining an apparent S. mansoni prevalence rate of 10% in an area estimated to have a natural rate of below 5% following two chemotherapy campaigns. To sustain interest and therefore accuracy among microscopists engaged on screening, known S. mansoni-positive stools were seeded, without their knowledge, among those collected in the field. The problems of achieving a desired level of seeding, and of a possible further dimension of the scheme are discussed.

Further observations from St Lucia on control of Schistosoma mansoni transmission by provision of domestic water supplies.

Individual households in five settlements were provided with piped water in a pilot scheme to investigate the effect on transmission of S. mansoni in St Lucia. Nearby comparison settlements, in the same valley, were provided with water through a public standpipe system. The incidence of S. mansoni infection among children decreased in the experimental area, leading to lower prevalence rates and lower intensity of infection in all age groups. Over the study period, indices of infection increased in the comparison settlements, but by the end of the period development was making those settlements less suitable for comparison purposes and some reduction in transmission was occurring.The changes in human infection rates were reflected in the results of studies with sentinel snails. In the experimental area, infection rates gradually fell owing to reduced water contact and consequently less contamination of the river and its banks, and possibly to the gradual reduction in contamination potential of the community with reduced prevalence and intensity of infection. It is suggested that a piped water supply be considered as a method of schistosomiasis control, but that the cost should not be debited only to the control of this disease since a clean water supply has other medical and social benefits.

Evaluation of an experimental mollusciciding programme to control Schistosoma mansoni transmission in St Lucia.

The size and number of colonies of Biomphalaria glabrata were reduced after four years of a surveillance/treatment snail control programme using an emulsifiable concentrate of niclosamide (25% active ingredient). Surveys among the human population showed that the incidence of new Schistosoma mansoni infections in 0-10 year-old children fell from 22% to 4.3%, while in a comparison area the incidence remained at 20%. With reduced transmission over four years, the prevalence of infection in a cohort of children examined in 1971 and 1975 fell from 34% to 23%. The fall in prevalence and intensity of infection led to a reduction of 66% in the index of potential contamination, which was reflected in a reduced rate of infection among sentinel snails and representative samples of B. glabrata collected during surveillance searches.The overall annual cost of the programme was US $3.24 per capita.

Quality control in laboratory investigations on Schistosoma mansoni on St Lucia, West Indies: a staff assessment scheme.

A method is described for the supervision of technicians engaged in microscopical screening of large numbers of stools for Schistosoma mansoni ova. The scheme presents graphically a regularly updated longitudinal evaluation of both individual and group standards of technical competence.