Identification of determinants of pesticide exposure among Kenyan agricultural workers using empirical modelling.

The influence of factors such as type of pesticides used, use of personal protective devices and hygienic behaviour on acetylcholinesterase inhibition and activity levels in red blood cells of agricultural workers was studied in four areas in Kenya. Empirical modelling techniques were used to identify and quantify factors affecting acetylcholinesterase inhibition and activity. Use of personal protective devices was almost non-existent in areas 3 and 4 where mainly subsistence farmers were studied. Differences in hygienic behaviour between areas were relative small. WHO Class I pesticides were mostly found in area 1 (mainly large farms growing flowers) which also had highest amounts of pesticide use and highest frequency of pesticide spraying. Despite widespread use of protective devices in this area significant inhibition occurred. It became unclear whether acetylcholinesterase inhibition occurred as a result of protective clothing soaked with pesticides, thereby increasing dermal exposure, or because of other (unmeasured) factors. Inhibition, however, could have been much worse without protective devices. In area 1, most workers wore boots, which were found to be protective only when combined with an overall; wearing boots alone led to increased inhibition. Access to a washing facility or bathing facility had a positive effect on acetylcholinesterase levels. However, washing of hands and bathing immediately after spraying seemed reactive behaviour rather than proactive behaviour. Spraying was found to lead to more profound acetylcholinesterase inhibition than mixing. Workers who sprayed WHO Class III pesticides had less acetylcholinesterase inhibition than workers spraying more toxic pesticides.

Pattern of Schistosoma mansoni infection after intervention in Mwea irrigation scheme in Kenya.

A longitudinal study of Schistosoma mansoni reinfection rate was carried out in an endemic area of Kenya, after intervention. Intervention measures applied involved chemotherapy, community mobilization to effect change in water contact habits and faecal disposal. This paper focuses on S. mansoni reinfection pattern over a two-year period. The age group 5-19 years showed an increasing trend of reinfection as compared to the 30-59 years age group. More than 50% in the 5-19 year age group had been reinfected by twelve months of follow-up. They were also responsible of 91% of all the egg-load and 83% of all the infections at the end of the study period. Since majority of the 5-19 year age group comprises school children, there is an urgent need of including issues related to schistosomiasis in the school curriculum especially in the endemic areas.

PIP: Schistosomiasis is a parasitic disease caused by blood flukes which live in the mesenteric and/or vesical veins of humans over a life span of several years. Cercariae are released by infected intermediate snail hosts into fresh water whose larvae then penetrate the skin of man when the individual contacts infected fresh water. Schistosomiasis is debilitating, setting in slowly and causing concern in its chronic stages. Chronic infection results in complications such as liver fibrosis and portal hypertension for Schistosoma mansoni and ureteric obstruction, bacterial infection, and cancer of the bladder for S. haematobium. In endemic areas, children have the highest prevalence and intensity of infection due to their more extensive contact with water relative to adults. Chemotherapy helps to control the disease, but population immigration, untreated pregnant women and very young children, and the selectiveness of control strategies make reinfection inevitable. This paper reports findings on the rate of reinfection with S. mansoni in Kirinyaga district, Kenya, between September 1983 and December 1988, after a prevention and control intervention. Schistosomiasis is endemic in that area of Kenya. Measures applied during the intervention included chemotherapy and community mobilization to effect change in water contact habits and faecal disposal. Individuals aged 5-19 years showed an increasing trend of reinfection compared to individuals aged 30-59 years, with more than 50% of subjects in the 5-19 year old age group being reinfected by twelve months of follow-up. The young age group also accounted for 91% of the egg-load and 83% of all infections at the end of the study period. The majority of the 5-19 year old age group comprises school children. An urgent need therefore exists to cover schistosomiasis-related issues in schools.

Comparative aetiology of childhood diarrhoea in Kakamega and Kiambu Districts, Kenya.

Two hundred diarrhoea specimens collected during January to February 1988, from rural children aged 0 to 60 months in Kakamega District were examined for bacteria, parasites and rotavirus. The results were compared with a sample of 184 diarrhoea specimens matched for month of collection, taken from data collected in the same manner from children in Kiambu District. The mean ages of children in the 2 samples did not differ significantly. There were significant differences in the prevalence of specific potential pathogens isolated in the 2 areas. Notably, A. lumbricoides and rotavirus were more common in Kakamega, while G. lamblia, Entamoeba histolytica, Trichomonas hominis, Cryptosporidium sp., Hymenolepis nana and EPEC were more common in Kiambu. There was no difference with respect to prevalence of Campylobacter sp. or Blastocystis hominis. Factors which were probably important in determining aetiological differences included climate, water sources, animal contact and crowding. The differences highlight the fact that general predictions about aetiology cannot be made from isolated studies.

PIP: A total of 200 loose or watery specimens of diarrhea collected during January and February 1988 from rural children aged 0 to 60 months (mean age of 17.9 months) in Kakamega District, Kenya, were examined for bacteria, parasites, and rotavirus. The results were compared with data from a sample of 184 diarrhea specimens collected during January and February 1986, in the same manner from children with a mean age of 19.7 months in Kaimbu District. Complete investigations were accomplished in 140 of 184 specimens in the Kiambu sample. The most common organism in the Kakamega sample was A. lumbricoides (31%) compared with Escherichia coli (EPEC, 26.4%) and G. lamblia and (26.1%) in the Kiambu sample. There was no Cryptosporidium or Hymenolepis nana isolated in the Kakamega sample, while their frequencies were 2.7% and 3.8%, respectively, in the Kiambu sample. A. lumbricoides and rotavirus were significantly more common in the Kakamega sample, while all the protozoa, including G. lamblia, Entamoeba histolytica, and Trichomonas hominis, were more commonly isolated in the Kiambu ample. The Kiambu sample involved significantly more persistent diarrheas: more than 8 days (18.8%) than the Kakamega sample (3.5%) (p 0.001). A total of 44/140 (31.4%) of diarrheas were negative for potential pathogens in the Kiambu sample compared with 67/200 (33.5%) in the Kakamega sample. Mixed infections were common in both samples in which pathogens were isolated, with 53/133 (39.8%) in Kakamega being mixed, compared with 51/96 (53.1%) in Kiambu. One specimen in Kakamega had 5 potential pathogens (rotavirus, EPEC, C. lamblia, A. lumbricoides, B. hominis), while 1 specimen in Kiambu harbored 7 (EPEC, Shigella, Campylobacter, E. histolytica, T. hominis, G. lamblia, B. hominis). The community etiology of childhood diarrhea appears to be influenced by many factors which encourage direct fecal-oral transmission including climate, water sources, animal contact, and crowding.

Prevalence and frequency of Giardia lamblia in children aged 0 to 60 months with and without diarrhoea.

Stool specimen results from children with diarrhoea and without diarrhoea, in a rural village community in Kenya, were analysed in order to compare prevalence and age frequency distributions of Giardia between the 2 groups. There was evidence for 2 age-related prevalence peaks for Giardia in children 60 months and below. Furthermore, there appeared to be a clear Giardia-diarrhoea relationship in the age group of 19 to 24 months.

PIP: Stool specimen results were analyzed from children with diarrhea and without diarrhea in a rural village in Kenya, Nderu, to compare the prevalence and age frequency distributions of Giardia between the two groups. Data for Giardia were available from the National Diarrhea Control Program (NDCP) for the period September 1985 to September 1986 for 608 diarrhea specimens. These data were compared to those from 408 stool specimens collected during four cross-sectional surveys in Nderu between July 1985 and October 1986 from children aged 0-60 months without diarrhea in 60 families. The impact of Giardia in childhood morbidity in communities where the organism is endemic remains elusive. The major problems encountered when defining the morbidity of Giardia in an endemic setting are the limitations of applying epidemiological methods where the organism is so frequent, and the phenomenon of poly-parasitism making it very difficult to pinpoint the effects of a single organism. It was nonetheless determined that a significant proportion of childhood diarrhea, at least among 19-24-month olds, is associated with and probably caused by Giardia. This increase in prevalence of Giardia in the 19-24-month group apparently leads to a second peak of Giardia-induced diarrhea at 37-48 months. This second peak is difficult to interpret.

Longitudinal study of young children in Kenya: intestinal parasitic infection with special reference to Giardia lamblia, its prevalence, incidence and duration, and its association with diarrhoea and with other parasites.

84 young children from a rural community, Nderu, in Kenya, were each followed for up to 10 months, from January to November 1987. Their ages ranged from 10 to 28 months over the period of study. Stools were obtained once a week, as were reports from the mothers about presence of abdominal complaints, including diarrhoea. A total of 2258 stools and 1873 reports were collected. 9 parasites were commonly encountered of which Giardia lamblia was the most frequent at 44.7%. The overall estimated number of new Giardia episodes per year per child was 2.77 +/- 2.22 SD and the mean estimated duration of infection was 75.25 +/- 73.84 SD days per child. The mean proportion of positive visits per child was 0.42 +/- 0.25 SD. Giardia trophozoites, Trichomonas hominis, Chilomastix mesnili, Entamoeba histolytica, Blastocystis hominis and Hymenolepis nana were all significantly associated with unformed stools and reports of diarrhoea. There was a significant probability of finding Giardia in stool within +/- 2 weeks of a report of diarrhoea. Poly-parasitism was common and several paired associations were significantly positive, particularly between species of amoebae. Quantity of Giardia in stool (expressed as a 0 to 5+ score) was suppressed both by type and number of other parasites present.

Intestinal parasites in a rural community in Kenya: cross-sectional surveys with emphasis on prevalence, incidence, duration of infection, and polyparasitism.

A cross-sectional survey of intestinal parasitic infection in a rural community, Nderu, in Kiambu District, Kenya, was carried out in 1985 by examining 1129 individuals from 203 households (about 25% of the total population). This was followed by 3 more cross-sectional surveys, in January, May and October 1986, of 56 families comprising 461 individuals, who had also participated in the first survey. In the first survey, 81.4% of the sample was positive for at least one intestinal parasite and 78% was positive for intestinal protozoa. 72.7% of those infected had multiple infections. The prevalence of most of the protozoa increased with age but that of Giardia lamblia peaked in the 0 to 4 year class at 35.5%. Females were infected more often with several of the protozoa, but males with Ascaris. People living in larger households were more often infected with Entamoeba histolytica and Iodamoeba butschlii, while the opposite was true of H. nana and tended to be for Giardia. Significant positive associations between parasite species were common at all surveys, especially among the amoebae. The majority of negative associations were for Giardia. Unformed stools were significantly associated with Giardia, Blastocystis, and trophozoites of Trichomonas hominis and Chilomastix mesnili. Endolimax nana and Entamoeba coli were found more often in formed stools. Estimates of daily incidence, and duration of infection in days, were calculated for 11 parasites. The longest mean estimated duration of infection for any species was 237 +/- S.D. 151.4 days for H. nana and the shortest was 41.6 +/- S.D. 0.4 days for T. hominis.

Mixed infections in childhood diarrhoea: results of a community study in Kiambu District, Kenya.

One thousand four hundred and twenty diarrhoea specimens from 846 children aged 0 to 60 months were collected and analysed for bacteria, parasites and rotavirus over a 16 month period, from June 1985 to September 1986 inclusive. The study was conducted in 4 villages situated in Kiambu District, Kenya. All the specimens were analysed for rotavirus and parasites, including Cryptosporidium. The majority of the specimens were analysed for enteropathogenic Escherichia coli (EPEC), Shigella, Salmonella, Campylobacter and Aeromonas. Only 387 specimens were analysed for enterotoxigenic E. coli (ETEC). However, of this proportion analysed for ETEC, 33% were positive. A total of 344 specimens were negative for any organisms while a further 140 were only positive for parasites which have been implicated as being pathogenic, including Ascaris lumbricoides, Hymenolepis nana, Trichomonas hominis and Blastocysts hominis were considered to be at least potentially pathogenic and capable of causing diarrhoea. An average of only 29.4% of these organisms occurred as single isolates. The remaining infections were mixed, with a maximum of 7 potentially pathogenic organisms occurring together in a single specimen. The associations of certain organisms were significant, notably Campylobacter with Giardia lamblia. Campylobacter with EPEC, EPEC with Ascaris, and G. lamblia with rotavirus. The latter was a negative association.

Cryptosporidiosis and childhood diarrhoea in a rural community in Kenya.

Cryptosporidiosis has come to recent prominence as a cause of diarrhoea throughout the world in both adults and children, producing either an acute self-limiting diarrhoea or a protracted chronic diarrhoea which can be fatal in immunosuppressed patients. This study was therefore conducted to assess the prevalence of the infection among children less than five years of age in a rural community in Kiambu District, Kenya. 1420 diarrhoea specimens from children less than five years which were processed for bacteriology and parasitology were also examined for Cryptosporidium oocysts, using the modified Ziehl-Neelsen (ZN) acid-fast stain, 3.8% of all the diarrhoea samples were positive for oocysts. 320 non-diarrhoeic stools from children in the same age group were also examined and were all negative for Cryptosporidium oocysts. The results of this study would imply that infection with Cryptosporidium is associated with acute childhood diarrhoea in Kenya.