Schistosoma mansoni in migrants entering South Africa from Moçambique--a threat to public health in north-eastern KwaZulu-Natal?

OBJECTIVES: To identify possible public health consequences of Schistosoma mansoni infections in migrants entering north-eastern KwaZulu-Natal and Mpumalanga and Northern Province from southern Moçambique. DESIGN: (i) Intestinal parasite surveys, one sample per person, within a 4-month period; (ii) temperature recordings and snail collections in an irrigation system. SETTING: North-eastern KwaZulu-Natal and Kruger National Park, Mpumalanga and Northern Province. PARTICIPANTS: Ninety-seven migrants (1-68 years) from north-eastern KwaZulu-Natal and 47 from the Kruger Park (1 - 70 years). MAIN OUTCOME MEASURES: The relatively high S. mansoni prevalence may cause problems on the rice paddy scheme in north-eastern KwaZulu-Natal. Ranges and prevalence rates of other parasites were recorded. RESULTS: S. mansoni prevalence in Moçambicans entering north-eastern KwaZulu-Natal was 14.4%, seven times more than in local residents. S. mansoni is not endemic to this region because most bodies of water become too warm for either the parasite or its snail host, Biomphalaria pfeifferi, to develop. Recordings in paddies suggest, however, that the rice modifies the temperature pattern as it grows and provides a suitable habitat for transmission. Migrants entering the Transvaal lowveld where S. mansoni is endemic may become more severely infected. Thirteen other parasite species were recorded from migrants entering KwaZulu-Natal and 8 from those entering Mpumalanga and Northern Province. CONCLUSIONS: The relatively high S. mansoni prevalence among migrants entering north-eastern KwaZulu-Natal may have public health implications as it could encourage transmission in a non-endemic area. The range of parasites carried by migrants entering KwaZulu-Natal, Mpumalanga and Northern Province was similar to that harboured by local people but prevalence rates were generally lower.

Assessment of the residual efficacy of lambda-cyhalothrin. 2. A comparison with DDT for the intradomiciliary control of Anopheles arabiensis in South Africa.

There are several factors that support the need to assess the efficacy of potential alternative insecticides to DDT for malaria vector control. The objectives of this study were to evaluate the persistence and efficacy against Anopheles arabiensis of lambda-cyhalothrin used as an intradomiciliary insecticide in daub huts and to compare its efficacy in this regard to DDT. Exit trap catches showed the population of An. arabiensis was high during the months of January to March, with a peak in February. During all months, the number caught leaving lambda-cyhalothrin-sprayed huts was markedly less than the number from both control and DDT-sprayed huts. The percentage survival of bloodfed mosquitoes ranged from a low of 55% caught leaving the lambda-cyhalothrin-sprayed huts, to 82% of those caught leaving DDT-sprayed huts. The percentage of bloodfed mosquitoes caught leaving huts was high (> 60%). The survival of unfed mosquitoes was low, even from the control huts (43%).

Assessment of the residual efficacy of lambda-cyhalothrin. 1. A laboratory study using Anopheles arabiensis and Cimex lectularius (Hemiptera: Cimicidae) on treated daub wall substrates from Natal, South Africa.

Laboratory assessment of the residual efficacy of lambda-cyhalothrin (Icon) 10% AI against Anopheles arabiensis and Cimex lectularius was carried out. The insecticide was applied to daub substrates, simulating the wall surface of houses from 3 areas within the endemic malaria area of Natal, South Africa. Variability in residual efficacy was found between different areas and appeared to correlate to organic content of the substrate. Residual efficacy against An. arabiensis ranged from as little as 2 wk in some areas to in excess of 14 wk in others. Residual efficacy against C. lectularius was 4 wk for all 3 areas, but was 10 wk in only 2 areas.

Morbidity from falciparum malaria in Natal/KwaZulu.

Plasmodium falciparum malaria is endemic in the northern KwaZulu areas of South Africa. The clinical morbidity produced by this parasite has not been studied since the institution of the present malaria control programme. Fifty-nine patients were prospectively studied at a peripheral clinic during the peak malaria season; symptoms and signs of the infection, parasite loads, haemoglobin values and leucocyte counts were recorded in all patients. Haemoglobin and leucocyte counts were also measured in 37 control subjects without malaria. The commonest symptoms were persistent headache (100%), rigors (98%) and myalgia (93%). None of the patients presented with coma, pulmonary oedema, hypoglycaemia or algid malaria. Splenomegaly was found in 49%, hepatomegaly in 20% and mental confusion in 5% of patients. Mean parasite load was 1.71% and 57% of patients had parasite loads of < 1%. Anaemia of < 10 g/dl was significantly more frequent (P < 0.0001) in the patient group than in the control group. Leucopenia (white cell count < 4.0 x 10(9)/l) was present in 12 of 50 patients in whom it was measured compared with 2 controls (P = 0.0175). The results show a wide range of morbidity, without severe complications as presenting manifestations. Symptomatic infection in the presence of low parasite loads suggests that there may be little or no immunity in this population.

Seroprevalence of HIV infection in rural South Africa.

OBJECTIVES: To establish the prevalence of HIV infection in rural South Africa and to investigate demographic factors that influence this prevalence. DESIGN: An anonymous HIV seroprevalence survey was performed in conjunction with a population-based malaria surveillance programme. SETTING: The rural area of northern Natal/KwaZulu, South Africa. PARTICIPANTS: A total of 5023 black African participants were recruited by malaria surveillance agents during house-to-house visits; each house in an endemic malaria area is visited approximately once every 6 weeks. Participants included 4044 healthy and 979 febrile individuals (i.e., suspected of having malaria). MAIN OUTCOME MEASURES: HIV-1 and HIV-2 serological status, degree of mobility, age and sex. RESULTS: Sixty of the 5023 blood specimens were confirmed to be HIV-1-antibody-positive by Western blot, an overall prevalence of 1.2% (95% confidence interval, 0.9-1.5). None of the specimens was positive for HIV-2 antibodies. After adjusting for age, presence of fever and migrancy, women had a 3.2-fold higher prevalence of HIV-1 infection than men. HIV-1 infection was approximately three times more common among subjects who had changed their place of residence recently (2.9 versus 1.0%, P < 0.01). CONCLUSIONS: The prevalence of HIV-1 infection is higher among women than men resident in rural Natal/KwaZulu, South Africa. This is at least in part the result of oscillatory migration, particularly of men who work in urban areas but have families and homes in rural areas. Migration is associated with a higher prevalence of HIV-1 infection, suggesting that improving social conditions so that families are not separated and become settled in their communities is one way to help reduce the spread of HIV-1.

PIP: As part of a population-based malaria surveillance program in late 1990, surveillance agents took blood samples from 979 people who had had a fever within the last 2 weeks and from 4044 healthy people during regular house-to-house visits in rural northern Natal/KwaZulu, South Africa, to determine HIV seroprevalence and risk factors of HIV infection. 60 (1.2%) people were HIV-1 seropositive. No one had HIV-2 infection. Febrile people had a 30% higher sex-adjusted relative risk (RR) of HIV-1 infection than healthy individuals, but this increase was insignificant. Women were at greater risk of HIV-1 infection than men (1.6% vs. 0.4%; age-adjusted RR = 3.8). In fact, this risk still existed when the researchers controlled for fever (RR = 3.75) and migrancy (RR = 3.2). The fall in the RR for women from 3.8 to 3.2 when controlled for migrancy suggested an underrepresentation of migrant male workers in the study sample. 2.3% of the women in their childbearing years (15-44) were HIV-1 seropositive, indicating an increased likelihood of transmission of HIV-1 to newborns. The youngest person afflicted with HIV-1 was a 12-year-old female and the oldest was a 66-year-old woman. No 10-to-19-year-old males tested HIV-1 positive, while 1.7% of the 10-to-19-year-old females did, suggesting that the young females had sex with older men. This may have indicated teenage prostitution and sexual abuse. 2.9% of the people who changed their place of residence within the last year (migrancy) had HIV-1 infection. For women it was linked to a 2.4 times higher RR (age-adjusted) of HIV-1 infection. For men, the age-adjusted RR was even greater (7.3). Even though HIV-1 seroprevalence was about 45% greater in areas crossed by the main national road than it was in other areas (1.3% vs. 0.9%), the difference was not significant. Since migrants were a key source of HIV-1 infection, improvement in social conditions, allowing families to live together and to settle in their communities, may reduce HIV-1 transmission.

Malaria control and levels of DDT in serum of two populations in Kwazulu.

Concentrations of p,p'-DDT, p,p'-DDE, and p,p'-DDD were determined in serum of members of households of two different areas of KwaZulu. Annual intradomiciliary application of DDT is used for the interruption of malaria transmission in one area (the exposed group) while the other served as the control. Demographic differences between the two groups resulted in significantly more females in the control group. The two groups were comparable with respect to age. Serum from household members living in DDT-treated dwellings had significantly higher (p less than .005) levels of sigma DDT and metabolites (mean sigma DDT 140.9 micrograms/l) than those from the control area (mean sigma DDT 6.04 micrograms/l). Percentage DDT was also significantly higher (p less than .05) in the exposed group (28.9%) than the control group (8.3%). sigma DDT for the 3-10 yr age interval (168.6 micrograms/l) was significantly higher (p less than .05) than the 20-29 (60.5 micrograms/l) and 30-39 (84.2 micrograms/l) yr age intervals. There seemed to be two groups with regard to accumulation and elimination. The age group 3-29 appeared to be eliminating DDT, most likely accumulated from contaminated breast milk, faster than they accumulated it. From around 29 yr of age accumulation predominated as the levels increased with age. Regression analysis suggested pharmacokinetic differences for DDE and DDT between the two groups. Liver function parameters between the two groups only differed significantly for gamma-glutamyl transferase (gamma GT) (p less than .005), but the influence of difference in alcohol consumption, which was significantly higher in the exposed group (p less than .0001), offered a better explanation. Those of the exposed group that consumed alcohol had a significantly higher (p less than .05) mean gamma GT level (41.5 IU/l) than those that did not (20.2 IU/l), but were not significantly different for sigma DDT (p greater than .05). The safety of DDT used in malaria control for subjects aged 3 and older was confirmed by the levels of DDT in serum when compared with other studies, which showed lack of any negative effects associated with these levels in adults, and an apparently normal liver function in the exposed and control groups.

In vitro confirmation of chloroquine-resistant Plasmodium falciparum malaria in KwaZulu.

In May 1987 and January 1988 the chloroquine sensitivity of Plasmodium falciparum in the Ubombo and Ingwavuma districts of KwaZulu was determined by a modified in vitro microtest in which the patients' plasma was replaced with non-immune human AB serum and the test plates were incubated in an atmosphere of 3% oxygen, 4% carbon dioxide and 93% nitrogen. A success rate of 74% was achieved using this technique. All of 23 successfully tested isolates from malaria patients reporting to clinics and a hospital in these areas were found to be resistant to chloroquine, schizogony being inhibited at 32 pmol per well in the majority of tests. Seventy-five per cent of the isolates obtained through active surveillance in the Ubombo district were found to be resistant in varying degrees. Malarial parasites collected from clinics and a hospital in the endemic area did not change markedly in their in vitro response to chloroquine during the 8-month period May 1987-January 1988.