Intestinal protozoa and intestinal helminthic infections in displacement camps in Sierra Leone.

Displacement and refugee camps provide ideal grounds for the transmission of parasites and increase the risk of acute respiratory infections, diarhoea diseases, and intestinal parasitic infection. Cryptosporidium parvum, Giardia lamblia, Entomoeba histolytica, Ascaris lumbricoides, hookworm infection, Schistosoma haematobium, S. mansoni and Strongyloides stercoralis are important cosmopolitan intestinal parasites that are common among children, the immunocompromised and displaced populations. Five hundred and eighty one residents from 5 Internally Displaced Persons (IDPs) Camps voluntarily participated in the study by providing stool and urine samples for analysis. The stool specimens were used for the detection of Cryptosporidium specific and Giardia specific antigens by the DMSO modified Acid-Fast and Trichrome-PLUS stain for C. parvum and G. lamblia and E. histoyltica respectively. Stool specimens for the demonstration of helminth eggs and larvae were prepared by the modified Kato technique. One hundred and seventy eight (31%) of the 581 camp residents that submited samples were children below 10 years of age and were selected because they were screened for various forms of malnutrition. However, the data on C. parvum and G. lamblia were included in the analysis for all parasites. More children were positive for G. lamblia (29%) than for C. parvum (10%) and 5% had double infection with both parasites. The antigen positive rate decreased with age for C. parvum and G. lamblia infections. Adult samples were also examined for the C. parvum, G. lamblia, E. histolytica, A. lumbricoides, hookworms, S. haematobium, S. mansoni and S. stercoralis. The prevalence of hookworm was highest at Parade Ground Camp (50%) and hookworm had the highest pevalence rate of 18% among the 581 IDP residents followed by S. mansoni (16.7%) and A. lumbricoides (15%). The overall prevalence of E. histolytica among the study population was 9.0%. The results of this study indicate that intestinal protozoan and helminth parasites are highly prevalent among camp residents in Sierra Leone with five (5) different helminth parasites demonstrated in the stool specimens of residents in the five IDP camps.

Analysis of west African hunters for foamy virus infections.

Foamy viruses are a genus of complex retroviruses that infect a wide variety of mammals. However, a clear association with any disease process has yet to be proven for these viruses. A higher human seroprevalence was reported in African populations, perhaps due to exposure to simian foamy viruses (SFV) endemic in primates. However, the earlier serologic surveys were not confirmed by studies employing nucleic acid amplification. Foamy virus infections of humans clearly do occur as rare zoonoses among primate center or laboratory workers exposed to captive primates or their blood. We sought to detect foamy virus infections in a cohort of humans also presumed to be exposed to SFV, i.e., West African hunters. We constructed recombinant vaccinia viruses that expressed human foamy virus (HFV) Gag or Env polyproteins in mammalian cells. The sera from 17 monkey hunters or several controls were tested in radioimmunoprecipitation assays (RIPAs) against the recombinant HFV proteins. Chimpanzee sera or HFV-positive human sera immunoprecipitated gp130, the HFV Env precursor, as well as p74, the HFV Gag polyprotein. None of the hunters' sera recognized both of these recombinant proteins. We then employed a nested polymerase chain reaction (PCR) analysis of the hunters' DNA but also failed to detect foamy virus infections. Therefore, by utilizing a recombinant RIPA and a nested PCR assay, we have not identified foamy virus infections occurring naturally in hunters exposed to wild monkeys in West Africa.

Delayed isotype switching in Dirofilaria immitis infection.

The anti-microfilarial immunoglobulin response in Dirofilaria immitis infection was investigated serially in a naturally infected dog. Spontaneous clearance of microfilariae was associated with IgM opsonizing antibodies which promoted in vitro killing of microfilariae by granulocytes. Over a 6- to 11-month period, there was a shift to a predominantly IgG response. The addition of fresh non-immune serum markedly enhanced killing mediated by both IgM and IgG. The findings document conversion from IgM to IgG isotype with chronic infection, and suggest that isotype switching in canine D. immitis infection is delayed relative to that seen in bacterial or viral infections.

Anti-Onchocerca volvulus immunoglobulin subclass response in children from Sierra Leone.

The humoral immune responses of a paediatric population of 224 children, 2-15 years of age, residing in an onchocerciasis endemic area of Sierra Leone, were studied to gain information that may be useful in the serodiagnosis of prepatent and low-level infections with Onchocerca volvulus. The antigen-specific levels of IgG and IgG4 were determined and evaluated in the context of the parasitological status of the child. Over 87% of the microfilaria-negative children had significant levels of antigen-specific antibodies against O. volvulus, suggesting that a large percentage of this paediatric population were harbouring prepatent or low-level infections. Over 60% of the children in the group that had detectable numbers of microfilariae in skin snips had elevated levels of O. volvulus-specific IgG4. In contrast, only 23% of the microfilaria-negative children had detectable IgG4 responses. The results presented here indicate that measures of O. volvulus-specific IgG4 may be a useful indicator of the parasitological status of children during the very early stages of onchocerciasis.

Mermithid (Nematoda: Mermithidae) parasitism of Simulium damnosum s.l. (Diptera: Simuliidae) in Sierra Leone and the need for vector control.

Females of Simulium damnosum Theobald s.l. were systematically collected at four sites in the Gorawa Chiefdom of Sierra Leone, West Africa, over a period of 15 mo from July 1986 to September 1987. The prevalence of mermithids infecting parous females varied from 0 to 7.9%, whereas the prevalence of mermithids in nulliparous females varied from 0 to 42.8%. The peak incidences of mermithid infection in nulliparous females occurred during the rainy season (15.2% in October 1986, 42.8% in August 1987). The high incidence of mermithids was associated with a high monthly biting rate, particularly during the month before the peak mermithid period (5,240 in September 1986, 4,878 in July 1987).

Integrated control of Onchocerca volvulus infection in a hyperendemic zone in Sierra Leone.

A simplified integrated method of onchocerciasis control involving mass chemotherapy with ivermectin, nodulectomy and health education was carried out in south central Sierra Leone. The prevalence of Onchocerca volvulus in the village community ranged from a low of 7.4% among the International School children to a high of 97.0% in Gbessebu. There was a significant (3-4%) overall reduction in the rate of infection after one year of ivermectin treatment (G = 2565.97, df = 11, P < 0.001). In addition, ivermectin treatment had a significant effect on the college community (G = 1168.21, df = 5, P < 0.001) and from year to year (G = 187.29, df = 1, P < 0.001), though the effect indicates the reduction varied between communities. Mass ivermectin treatment significantly (G = 1 3.79, df = 1, P < 0.005) reduced the rate of infection among school children, while the prevalence and intensity of infection was reduced by nodulectomy. Health education involving the community gave us an entry point and allowed us to gain the maximum cooperation and participation from the communities.

Intestinal helminth infections in rural school children in Njala, Sierra Leone.

In a survey of five primary schools and one secondary school in and around the Njala University College environment, in Southern Sierra Leone, 1820 school children were examined. Ascaris lumbricoides was the most common helminth encountered (33.3%) followed by Trichuris trichiura (14.6%) and hookworm infection (10.4%). There was striking differences in the rate of infection between the various schools with the International School being the least affected by all parasites. Multiple infections were quite common, with 53.1% having one type of helminth infection, 40% had two types of helminth infections, while 6.9% had three or more helminth infections. School screening should be an important component of Primary Health Care in Sierra Leone since it offers good opportunity for disease surveillance, health education and early detection and treatment of infections before they become chronic.

The head louse in Sierra Leone: an epidemiological study among school children, in the Njala area.

A survey of five primary schools in the Njala area, Sierra Leone showed that Pediculus humanus capitis infestation is wide-spread. The overall prevalence was 6.8% among 1007 school children examined. Infestation rates varied between schools from 1.4% to 14.6% and the prevalence of infestation increased with age, from 3.1% among class I children to 10.2% among class IV and decreased to 4.9% among class VI children. Females had a higher infestation rate (8.3%) than their male counterparts (5.4%). The infestation rate was higher' in children whose fathers were Farmers (9.4%) followed by Traders (7.8%), Artisans (6.5%) and Professionals who had the lowest infestation rate of (5.8%). Sharing of beds, beddings and combs had a significant effect (P < 0.01) on the rate of infestation. The infestation was light, therefore, impetigo was minimal. Overcrowding at home is the main factor facilitating the transmission of the infestation from one head to another among these children.

High prevalence of bedbugs Cimex hemipterus and Cimex lectularis in camps for internally displaced persons in Freetown, Sierra Leone: a pilot humanitarian investigation.

The prevalence of bedbugs Cimex hemipera and C. lectularis was investigated in camps for the internally displaced persons (IDPs) in Freetown, Sierra Leone. Two hundred and thirty eight rooms were searched during the day and at night, and 233 (98%) of those rooms in 30 booths were infested with different life cycle stages of bedbugs. There hundred and ninety-eight (68%) of the bedbugs were adults, 145 (24.8%) were nymphs of various instars, and 41 (7%) were clusters of eggs. Significantly (P > 0.05) more bedbugs were recovered during the night inspections 64.6% as compared to 35.4% during the day inspections. In addition, more adult bedbugs were recovered at night than during the day, a manifestation of their peak feeding period. Of the total of 570 adults and nymphs collected and identified, 320 (56.1%) and 250 (43.9%) were Cimex lectularis and Cimex hemipterus respectively. Clinical examination of 221 individuals living in the booths during 3 consecutive weeks of examinations and treatment for conditions suggestive of bedbug infestation (bites and skin reactions as well as treatments for other health and medical conditions) showed that 196 (86%) had wheals as a direct result of bedbug bites. The data of this pilot humanitarian investigation shows a high prevalence of bedbug infestation in these displacement camps. It is recommended that some control measures be instituted, like residual insecticide application along with integrating control methods within the primary health care system, because bedbugs are a source of great irritation and sleepless nights that could lead to stress.

Saulea vitrea and low prevalence of schistosomiasis.

Thirty-six sties, including pools, small streams, large rivers, and rice fields swamps were examined for the intermediate snail hosts of schistosomiasis and other mollusca in 19 villages spanning 4 chiefdoms in Sierra Leone. Half of the Saulea vitrea collected were examined for possible infection and none was found to be infected. In addition, we examined 785 stool and 913 urine samples from children living in the villages and found low prevalence and intensity of S. haemotobium (1.8%; 1.9XG) and S. mansoni (1.9%; 2.1XG) respectively. The low prevalence and intensity of infection with schistosomiasis where S. vitrea is in abundance suggest some effect of S. vitrea on schistosome snail intermediate host, but the mechanism remains unknown.

Intestinal parasitic infections among rural farming communities in eastern Sierra Leone.

A study carried out in four rural, mainly farming villages in the Gorama Chiefdom, Kono District, Eastern Sierra Leone revealed that intestinal helminth infections are prevalent in this area of Sierra Leone. Out of the 1164 persons of all ages who were examined, 853 (73.5%) proved positive for at least one intestinal helminth infection. Ascaris lumbricoides was the most common helminth encountered (37.5%), followed by hookworms, 12.9%; Trichuris trichiura, 12.6%; Schistosoma mansoni, 5.6%; Strongyloides stercoralis, 3.8%; tapeworms 1.0%, and multiple infections were common. Adults used poorly built pit latrines, while children defecated indiscriminately and unsupervised around houses and in the nearby bush. In addition, in most of the villages, domestic water was obtained from polluted streams and rivers. Only one village had protected pipe borne water supply. The high prevalence of intestinal helminth infections in this area results from constant infection and reinfection caused by poor sewage disposal, poor environmental health, and the low socioeconomic status prevailing in these communities.

Inland valley swamp rice development: malaria, schistosomiasis, onchocerciasis in south central Sierra Leone.

The prevalence of malaria, schistosomiasis and onchocerciasis was determined in 1,106 residents of five villages in the Moyamba District, Southern Sierra Leone, to determine whether inland valley swamp (IVS) development was associated with changes in the prevalence of malaria, schistosomiasis and onchocerciasis in these villages. These parasitic diseases were studied in four villages receiving IVS, Food and Agricultural Organization (FAO) assistance and in one village not receiving FAO assistance. Malaria was the most prevalent infection, detected in 42.6% of the persons examined, followed by O. volvulus (17.7%), S. haematobium (0.6%) and S. mansoni (0.3%). Plasmodium falciparum accounted for 90.4% of the malaria infections, followed by P. malaria (2.1%), P. ovale (0.5%), and mixed infections (7.0%). The trend of infection to O. volvulus increased significantly with an increase in age. S. haematobium (0.6%) and S. mansoni (0.3%) infections were low and no Biomphalaria pfeifferi and Bulinus globosus were found in 33 IVS development swamps examined. These data indicate that IVS development is associated with an increase in the prevalence of malaria infection, but not in the prevalence of O. volvulus, S. haematobium and S. mansoni.

Filariasis in the Kaiyamba Chiefdom, Moyamba District Sierra Leone: an epidemiological and clinical study.

In a cross-sectional epidemiological and clinical study of human filariasis, 630 individuals were examined for Onchocerca volvulus, Wuchereria bancrofti and Mansonella perstans infections in five communities in the Kaiyamba Chiefdom, Moyamba District, Sierra Leone. The overall prevalence of O. volvulus infection in males 144(39.1%) and females 94(35.9%) was not significantly different and the sex prevalence rate between communities was also not significant (G = 3, d.f. = 4, P > 0.05). Prevalence of O. volvulus was significantly lower (G = 42.331, d.f. = 5, P < 0.001) in the 5-9 age group (13.3%) compared to the 40-49 age group (61.9%). Sixty-four (10.2%) and 38(6.0%) of individuals examined were positive for W. bancrofti and M. perstans infections respectively and prevalence of both infections in the five communities was not significant. Mixed infections with the all three filaria parasites were recorded in 10(3.2%) of the individuals. One hundred and sixty-four (71.3%) clinical cases due to W. bancrofti were inflammatory in nature; 36.5% were chronic, of which, 26.6% were hydroceles and 9.4% involved elephantiasis of both the scrotum and the lower legs. All 19(3.0%) of M. perstans-related clinical cases were inflammatory. Ninety-three(63.3%) of O. volvulus positive individuals that presented symptoms were inflammatory in nature, 14(9.5%) had ocular symptoms and 57(38.8%) had subcutaneous nodules. These data indicate that infections due to O. volvulus, W. bancrofti and M. perstans may be of public health importance in Sierra Leone.

Onchocerca Volvulus infection in Sierra Leone: relation between prevalence, intensity of infection, and ocular problems in a 'forest' region.

A two-year longitudinal study carried out in five villages in a forest region of Gorama Chiefdom, Kono District, Sierra Leone, revealed that infection with Onchocerca volvulus was hyperendemic, the overall rate of infection being 61.6%. Prevalence rose from 28.6% in the 1-5-year age group, peaking among the 21-30-year age group (82.5%) and then levelling off. The intensity of infection though low, peaked in the 31-40-year-old males and in the 41-50-year-old female cohorts. The iliac crest was more sensitive for microfilarial (mf) recovery than the shoulder and the outer canthus. The majority of the nodules were located in the pelvic region. Microfilariae invasion of the eye was low, with low anterior chamber lesions but high posterior chamber lesions comprising mainly optic atrophy and choroidoretinitis. The rate of blindness was 1.6%, ocular onchocerciasis being the leading cause of blindness followed by cornea opacities.

Parasitological and clinical studies on Wuchereria bamcrofti infectionin Moyamba District, Sierra Leone.

A total of 302 people were examined in 3 villages in the Moyamba District, Sierra Leone of microfilaria (mf) and clinical signs of Wuchereria bancrofti infection. Mf rates were 34.5% and 31.8% for Bonganema, Old Mosongo and Pelewahun respectively. The average mf rate of those examined was 34.8%. Analysed by age and sex, the highest mf rates were observed in males of age >/=21 years (46 - 56%). The relative risk of infection was significantly lower (P<0.000) for 5-10 year olds than 11+ year old individuals. Clinical studies of 284 individuals of age >/=11 years showed that recurrent fever was the commonest clinical sign observed and the rate was 5.9%. For the ages >/=41 years, the recurrent fever was 10%. The average hydrocele and elephantiasis rates were 2.5% and 1.1% respectively. For the ages >/=41 years, the hydrocele and elephantiasis rates were 4% and 3% respectively, indicating that Filariasis is an important public health problem in the area. Annual mass treatment of the study area residents with ivermectin for onchocerciasis has begun. Ivermectin has been reported to be effective for control of lymphatic Filariasis. The displacement of the population due to the undeclared war in the area will certainly negate the effects of the mass treatment programme.

It all began with Ronald Ross: 100 years of malaria research and control in Sierra Leone (1899-1999).

It was in Sierra Leone, 100 years ago in 1899, that human malarial parasites were first observed in wild-caught Anopheles gambiae and An. funestus, the principal vectors of malaria in Africa. In the same year, Ronald Ross initiated the first antilarval measures for malaria control. This paper reviews 100 years of malaria field research and control in Sierra Leone, which became known as the 'White Man's Grave' in the 19th century largely because of the high malaria-related mortality amongst Europeans living there. The establishment of a field laboratory for the Liverpool School of Tropical Medicine in Freetown in 1920 made Sierra Leone the centre for malaria field research in Africa up to and during the Second World War. Eminent malariologists including Ronald Ross, Samuel Christophers, George Macdonald, Leonard Bruce-Chwatt, Brian Maegraith, Ian Macgregor, Brian Greenwood and Michael Service visited Sierra Leone for malaria-related activities. This review highlights the tremendous efforts made towards defining the epidemiological picture of the disease and the most effective means of combatting it. Malaria control in Sierra Leone, as in many other parts of the world, used to be based largely on mosquito eradication. However, experience gained over the past 100 years has shown that mosquito control is often not cost-effective in areas where the interruption of transmission cannot be sustained. Emphasis should now be on early diagnosis, treatment with effective antimalarials, and the selective use of preventive measures including vector control and insecticide-treated materials where they can be sustained.

Onchocerca volvulus: application of the polymerase chain reaction to identification and strain differentiation of the parasite.

Previous studies have demonstrated that the genome of Onchocerca volvulus contains a variable tandemly repeated DNA sequence family with a unit length of 150 bp. The variability of the 150-bp family has been exploited to develop O. volvulus strain and species specific DNA probes. Application of these DNA probes to the study of the epidemiologically most significant life cycle stages of the parasite has been confounded by several obstacles. These include the relative insensitivity of some of the DNA probes and the difficulty in releasing genomic DNA from infective larvae and skin microfilariae in a form that may be directly detected by hybridization to the probes. DNA sequence comparison of 18 known examples of the 150-bp repeat has been used to develop two populations of degenerate oligonucleotides. These oligonucleotides have been shown to support the amplification of the 150-bp repeat family from Onchocerca DNA, using the polymerase chain reaction. Both strain and species specific members of the repeat family are faithfully amplified, allowing characterization of a parasite on the basis of hybridization of the PCR amplification products to the previously developed DNA probes. This method is shown to be applicable to all diagnostically important forms of the parasite, including adults, infective larvae, and skin microfilariae. In addition, the method is capable of detecting O. volvulus infective larvae directly in extracts of blackfly vectors.

Parasitologic survey of Onchocerca volvulus infection in the Nimiyama Chiefdom, Kono District, Sierra Leone.

Infection due to Onchocerca volvulus was investigated in the Nimiyama Chiefdom, Kono District, Sierra Leone, where Simulium damnosum s.l. is known to breed but no data on the prevalence and intensity of O. volvulus infection exists. Of the 735 individuals sampled by the skin snip method in five villages, 471 (64%) were infected. The infection rate for males was significantly (p less than 0.05) higher than that of the females. Two hundred and ninety-one (70.0%) of the 416 males skin snipped and 180 (56.0%) of the 323 of their female cohorts were infected. The intensity of infection increased with age, with the younger cohorts presenting lower microfilarial density (MFD). Palpable nodules were observed in 230 (48.4%) of individuals found positive for skin microfilariae and in 37 (5.0%) individuals found negative for skin microfilariae. It is concluded that O. volvulus infection is mesoendemic in the Nimiyama Chiefdom, with the intensity of infection increasing with age.

Apparent drug failure following artesunate treatment of Plasmodium falciparum malaria in Freetown, Sierra Leone: four case reports.

Four cases of Plasmodium falciparum malaria who presented in Sierra Leone in November-December 2000 apparently failed to respond to treatment with artesunate. Three (75%) of the cases fulfilled the World Health Organization's criteria for late treatment failure. Although artesunate ranks only sixth as the first-line drug used by clinicians for the treatment of uncomplicated malaria in Sierra Leone, it is widely sold over the counter in pharmacies in the country. The indiscriminate and injudicious use of artesunate among the Sierra Leonean population is likely to increase the level and frequency of resistance among the local strains of P. falciparum. It is recommended that artesunate be reserved for patients who fail to respond to treatment with another of the antimalarial drugs available. Even then, the artesunate should preferably be used in combination with other, longer-acting antimalarial drugs, to slow the development of further resistance.