Molecular identification of zoonotic hookworms in dogs from four counties of Kenya.

All canine hookworms are known to be zoonotic, causing infections ranging from transient skin irritations to prolonged 'creeping eruptions', eosinophilic enteritis and even patent intestinal infections. There is little information on canine hookworm species and their public health significance in sub-Saharan Africa. This study determined the prevalence and species of hookworms in dogs from different climatic zones of Kenya. Dog faecal samples were collected from the environment, and hookworm eggs were isolated by zinc chloride flotation and subjected to DNA extraction. Polymerase chain reaction (PCR) assays targeting the internal transcribed spacer (ITS) 1 and 2, 5.8S and 28S ribosomal RNA of Ancylostoma spp. and Uncinaria stenocephala were performed, and hookworm species were identified by PCR-restriction fragment length polymorphism (RFLP) or DNA sequencing. Hookworm eggs were detected by microscopy in 490/1621 (30.23%, 95% CI 28.01-32.54) faecal samples. Estimates of faecal prevalence were high in counties receiving higher rainfall (Narok 46.80%, Meru 44.88%) and low in those with a more arid climate (Isiolo 19.73%, Turkana 11.83%). In a subset of 70 faecal samples, Ancylostoma caninum (n = 59) was the most common species, followed by A. braziliense (n = 10) and A. cf. duodenale (n = 1). This study reports for the first time the detection of A. cf. duodenale in dog faeces and zoonotic hookworm species in Kenyan dogs. These findings emphasize the need for control measures such as enforcing laws for restraining stray dogs, regular deworming of dogs, and public health awareness programmes aimed at informing communities on outdoor use of footwear.

Global spread and genetic variants of the two CYP9M10 haplotype forms associated with insecticide resistance in Culex quinquefasciatus Say.

Insecticide resistance develops as a genetic factor (allele) conferring lower susceptibility to insecticides proliferates within a target insect population under strong positive selection. Intriguingly, a resistance allele pre-existing in a population often bears a series of further adaptive allelic variants through new mutations. This phenomenon occasionally results in replacement of the predominating resistance allele by fitter new derivatives, and consequently, development of greater resistance at the population level. The overexpression of the cytochrome P450 gene CYP9M10 is associated with pyrethroid resistance in the southern house mosquito Culex quinquefasciatus. Previously, we have found two genealogically related overexpressing CYP9M10 haplotypes, which differ in gene copy number (duplicated and non-duplicated). The duplicated haplotype was derived from the non-duplicated overproducer probably recently. In the present study, we investigated allelic series of CYP9M10 involved in three C. quinquefasciatus laboratory colonies recently collected from three different localities. Duplicated and non-duplicated overproducing haplotypes coexisted in African and Asian colonies indicating a global distribution of both haplotype lineages. The duplicated haplotypes both in the Asian and African colonies were associated with higher expression levels and stronger resistance than non-duplicated overproducing haplotypes. There were slight variation in expression level among the non-duplicated overproducing haplotypes. The nucleotide sequences in coding and upstream regions among members of this group also showed a little diversity. Non-duplicated overproducing haplotypes with relatively higher expression were genealogically closer to the duplicated haplotypes than the other non-duplicated overproducing haplotypes, suggesting multiple cis-acting mutations before duplication.

Geographical Distribution of Aedes aegypti aegypti and Aedes aegypti formosus (Diptera: Culicidae) in Kenya and Environmental Factors Related to Their Relative Abundance.

The mosquito Aedes aegypti (L.) is the primary vector of various infectious viruses and is typified by a polymorphic color and abundance of white scales on the body. It has been conventionally separated into two subspecies, Ae. aeg. formosus (Walker) (Aaf) and Ae. aeg. aegypti (L.) (Aaa), with Aaf considered a 'sylvan' form and Aaa a 'domestic' form. Because the two subspecies show different susceptibilities to dengue viruses it is important to understand their distribution. In this study, we collected larvae from artificial and natural habitats in southern Kenya and reared them to adults to morphologically identify subspecies. We describe the geographical distribution and relative abundance of Aaa and Aaf in Kenya, and estimate the environmental factors associated with their distributions by GIS using climate and environment data. A total of 5,243 Ae. aegypti adults were collected from 249 sites, with Aaa accounting for 22% of the specimens. The relative abundance of Aaa was higher in coastal areas versus sites in western Kenya. Aaa abundance was also higher in urbanized than forested areas, which is consistent with known ecology. In contrast and inconsistent with previous studies, both Aaa and Aaf were sympatric in artificial and natural habitats. The high relative abundance of Aaa in coastal areas might derive from old populated cities, climate, and/or introduction from abroad.

Chronic clinical manifestations related to Wuchereria bancrofti infection in a highly endemic area in Kenya.

Clinical examinations were conducted in an effort to provide baseline data for a pilot filariasis elimination programme implemented in a Wuchereria bancrofti-endemic focus in Malindi district, Kenya. Of 186 males aged 15 years and above examined, 64 individuals (34.4%) had hydrocele, and the prevalence of the manifestation in those above 40 years old was 55.3%. The prevalence of leg lymphoedema in persons aged 15 years and above was 8.5%, with a higher rate in males (12.6%) than in females (5.7%). The overall prevalence of inguinal adenopathy was 8.6%, and males had a significantly higher (12.9%) prevalence of adenopathy than females (5.1%) (P<0.001). The data in the present study provided support for consideration of filarial infection as a possible cause of inguinal lymphadenopathy in bancroftian filariasis-endemic areas. The results of this study also indicate that lymphatic filariasis is a serious public health problem in the northern coastal areas and morbidity control programmes should be implemented to alleviate the suffering of those affected.

Modelling strategies to break transmission of lymphatic filariasis--aggregation, adherence and vector competence greatly alter elimination.

BACKGROUND: With ambitious targets to eliminate lymphatic filariasis over the coming years, there is a need to identify optimal strategies to achieve them in areas with different baseline prevalence and stages of control. Modelling can assist in identifying what data should be collected and what strategies are best for which scenarios. METHODS: We develop a new individual-based, stochastic mathematical model of the transmission of lymphatic filariasis. We validate the model by fitting to a first time point and predicting future timepoints from surveillance data in Kenya and Sri Lanka, which have different vectors and different stages of the control programme. We then simulate different treatment scenarios in low, medium and high transmission settings, comparing once yearly mass drug administration (MDA) with more frequent MDA and higher coverage. We investigate the potential impact that vector control, systematic non-compliance and different levels of aggregation have on the dynamics of transmission and control. RESULTS: In all settings, increasing coverage from 65 to 80 % has a similar impact on control to treating twice a year at 65 % coverage, for fewer drug treatments being distributed. Vector control has a large impact, even at moderate levels. The extent of aggregation of parasite loads amongst a small portion of the population, which has been estimated to be highly variable in different settings, can undermine the success of a programme, particularly if high risk sub-communities are not accessing interventions. CONCLUSION: Even moderate levels of vector control have a large impact both on the reduction in prevalence and the maintenance of gains made during MDA, even when parasite loads are highly aggregated, and use of vector control is at moderate levels. For the same prevalence, differences in aggregation and adherence can result in very different dynamics. The novel analysis of a small amount of surveillance data and resulting simulations highlight the need for more individual level data to be analysed to effectively tailor programmes in the drive for elimination.

Associations between school- and household-level water, sanitation and hygiene conditions and soil-transmitted helminth infection among Kenyan school children.

BACKGROUND: Soil-transmitted helminths, a class of parasitic intestinal worms, are pervasive in many low-income settings. Infection among children can lead to poor nutritional outcomes, anaemia, and reduced cognition. Mass treatment, typically administered through schools, with yearly or biannual drugs is inexpensive and can reduce worm burden, but reinfection can occur rapidly. Access to and use of sanitation facilities and proper hygiene can reduce infection, but rigorous data are scarce. Among school-age children, infection can occur at home or at school, but little is known about the relative importance of WASH in transmission in these two settings. METHODS: We explored the relationships between school and household water, sanitation, and hygiene conditions and behaviours during the baseline of a large-scale mass drug administration programme in Kenya. We assessed several WASH measures to quantify the exposure of school children, and developed theory and empirically-based parsimonious models. RESULTS: Results suggest mixed impacts of household and school WASH on prevalence and intensity of infection. WASH risk factors differed across individual worm species, which is expected given the different mechanisms of infection. CONCLUSIONS: No trend of the relative importance of school versus household-level WASH emerged, though some factors, like water supply were more strongly related to lower infection, which suggests it is important in supporting other school practices, such as hand-washing and keeping school toilets clean.

Evaluation of ICT filariasis card test using whole capillary blood: comparison with Knott's concentration and counting chamber methods.

An immunochromatographic card test (ICT) that uses fingerprick whole blood instead of serum for diagnosis of bancroftian filariasis has recently been developed. The card test was validated in the field in Kenya by comparing its sensitivity to the combined sensitivity of Knott's concentration and counting chamber methods. A total of 102 (14.6%) and 117 (16.7%) persons was found to be microfilaremic by Knott's concentration and counting chamber methods, respectively. The geometric mean intensities (GMI) were 74.6 microfilariae (mf)/ml and 256.5 mf/ml by Knott's concentration and counting chamber methods, respectively. All infected individuals detected by both Knott's concentration and counting chamber methods were also antigen positive by the ICT filariasis card test (100% sensitivity). Further, of 97 parasitologically amicrofilaremic persons, 24 (24.7%) were antigen positive by the ICT. The overall prevalence of antigenemia was 37.3%. Of 100 nonendemic area control persons, none was found to be filarial antigen positive (100% specificity). The results show that the new version of the ICT filariasis card test is a simple, sensitive, specific, and rapid test that is convenient in field settings.

Bancroftian filariasis in Kwale district, Kenya.

OBJECTIVE: To determine the prevalence of Wuchereria bancrofti infection in an area designated for filariasis control trial. DESIGN: A cross-sectional survey. SETTING: Three villages in Kinango location, Kwale district, Coast Province, Kenya. SUBJECTS/PARTICIPANTS: Oral informed consent to participate was obtained from adults and parents or guardians of children below fifteen years of age. MAIN OUTCOME MEASURES: Microfilaraemia prevalences, microfilarial densities and clinical manifestations. RESULTS: The overall prevalence of microfilaraemia in the population was 16.4%. The prevalence of microfilaraemia was age-dependent and the overall microfilarial density (MFD) was 69.4 mf/ml (geometric mean) and significantly higher in males (95.8 mf/ml) than in females (48.6 mf/ml) (p < 0.05). The prevalence of clinical signs of infection was also age-dependent with elephantiasis being significantly higher in females (2.3%) than in males (0.9%) (p < 0.05). Among the males, the major clinical manifestation was hydrocele (10.4%). CONCLUSION: These findings show high prevalence of bancroftian filariasis in Kwale district and warrant similar studies followed by implementation of intervention measures to reduce transmission in all areas of endemicity in the Coast Province.

A survey for Echinococcus spp. of carnivores in six wildlife conservation areas in Kenya.

To investigate the presence of Echinococcus spp. in wild mammals of Kenya, 832 faecal samples from wild carnivores (lions, leopards, spotted hyenas, wild dogs and silver-backed jackals) were collected in six different conservation areas of Kenya (Meru, Nairobi, Tsavo West and Tsavo East National Parks, Samburu and Maasai Mara National Reserves). Taeniid eggs were found in 120 samples (14.4%). In total, 1160 eggs were isolated and further analysed using RFLP-PCR of the nad1 gene and sequencing. 38 of these samples contained eggs of Echinococcus spp., which were identified as either Echinococcus felidis (n=27) or Echinococcus granulosus sensu stricto (n=12); one sample contained eggs from both taxa. E. felidis was found in faeces from lions (n=20) and hyenas (n=5) while E. granulosus in faeces from lions (n=8), leopards (n=1) and hyenas (n=3). The host species for two samples containing E. felidis could not be identified with certainty. As the majority of isolated eggs could not be analysed with the methods used (no amplification), we do not attempt to give estimates of faecal prevalences. Both taxa of Echinococcus were found in all conservation areas except Meru (only E. felidis) and Tsavo West (only E. granulosus). Host species identification for environmental faecal samples, based on field signs, was found to be unreliable. All samples with taeniid eggs were subjected to a confirmatory host species RLFP-PCR of the cytochrome B gene. 60% had been correctly identified in the field. Frequently, hyena faeces were mistaken for lion and vice versa, and none of the samples from jackals and wild dogs could be confirmed in the tested sub-sample. This is the first molecular study on the distribution of Echinococcus spp. in Kenyan wildlife. The presence of E. felidis is confirmed for lions and newly reported for spotted hyenas. Lions and hyenas are newly recognized hosts for E. granulosus s.s., while the role of leopards remains uncertain. These data provide the basis for further studies on the lifecycles and the possible link between wild and domestic cycles of cystic echinococcosis in eastern Africa.

Evaluation of effectiveness of diethylcarbamazine/albendazole combination in reduction of Wuchereria bancrofti infection using multiple infection parameters.

OBJECTIVES: To evaluate the effect of multiple rounds of annual single dose of DEC (6 mg/kg) or albendazole (400mg) given alone or in combination on Wuchereria bancrofti microfilaraemia, anti-filarial IgG1 and IgG4 and antigenaemia. METHODS: A total of 170 participants were randomly assigned to albendazole (n = 62), DEC (n = 54), and DEC plus albendazole (DEC/ALB) combination (n = 54). Blood samples were collected at pre-treatment in 1998, at 1 week and 6 months after the first treatment and thereafter before subsequent treatments in 1999 and 2000. Effects of treatment on W. bancrofti infection were determined by changes in levels of microfilaraemia, antifilarial antibodies and circulating filarial antigen. RESULTS: Comparison of geometric mean microfilariae intensities between DEC/ALB combination and DEC or albendazole single therapy groups after two rounds of annual treatment and 24 months follow-up showed that combination therapy resulted in a greater reduction of microfilaraemia than single therapy with either albendazole (p < 0.001) or DEC alone (p = 0.146). The overall levels of anti-filarial antibodies decreased significantly (p = 0.028 for IgG1 and p < 0.043 for IgG4) in all treatment groups at 24 months follow-up. Additionally, overall reduction in geometric mean circulating filarial antigen levels at 24 months was 44%, 60% and 85% for albendazole, DEC and DEC/ALB groups, respectively. CONCLUSIONS: These study findings suggest that albendazole improved efficacy of DEC and mass administration of a combination of the two drugs would therefore enhance the interruption of transmission of W. bancrofti in endemic areas. This information has important implications for the ongoing Global Program for Elimination of Lymphatic Filariasis.

Impact of two rounds of mass treatment with diethylcarbamazine plus albendazole on Wuchereria bancrofti infection and the sensitivity of immunochromatographic test in Malindi, Kenya.

Annual single-dose mass treatment of endemic populations with a combination of either diethylcarbamazine (DEC) or ivermectin plus albendazole is recommended as the mainstay of lymphatic filariasis elimination programmes. We evaluated the impact of two rounds of annual mass drug administration (MDA) of DEC and albendazole on bancroftian filariasis in a pilot elimination programme in an endemic area of Kenya. Overall prevalence of microfilaraemia decreased by 65.4%, whereas community microfilarial load decreased by 84% after the two MDAs. The prevalence of parasite antigenaemia determined by immunochromatographic test (ICT) declined significantly by 43.5% after the two MDAs. We also studied the effect of mass treatment on the sensitivity of the ICT. Although the sensitivity of the test before treatment was high (89.9%; kappa=0.909) sensitivity was lower after two MDAs (59.3%; kappa=0.644). The finding raises concern about the reliability of the ICT in long-term monitoring of infection and for establishing programmatic endpoints. The results of the present study indicate a relatively high effectiveness of MDA using a DEC/albendazole combination against Wuchereria bancrofti infection and, therefore, it may be a useful strategy to eliminate lymphatic filariasis in onchocerciasis-free areas.

Immuno-parasitological assessment of bancroftian filariasis in a highly endemic area along the River Sabaki, in Malindi district, Kenya.

Lymphatic filariasis is endemic in the coastal areas of Kenya, with four major foci identified in the early 1970s. The prevalence and intensity of Wuchereria bancrofti infection, together with antifilarial antibody responses, were assessed in a historically highly endemic focus along the River Sabaki, in Malindi district. The prevalences of microfilaraemia and antigenaemia (detected by Og4C3 ELISA) were >20% and >40%, respectively, and both increased steadily with age. The high prevalences of antifilarial IgG1 (86%) and IgG4 (91%) responses indicate that most people living in this setting are exposed to W. bancrofti infection. The children investigated had higher levels of antifilarial IgG1 than the adults. The results of this study, based on a battery of currently available parasitological and immunological methods, provide an epidemiological update on lymphatic filariasis on the northern Kenyan coast. They show that the River Sabaki area is still an important focus for bancroftian filariasis and highlight the importance of implementing an elimination programme, to interrupt the transmission of W. bancrofti in all areas of endemicity in Kenya. The detailed baseline data collected in the River Sabaki area make the communities studied ideal as sentinel sites for epidemiological monitoring and the evaluation of the impact of mass drug administrations to eliminate lymphatic filariasis.

Community-directed Treatment of Lymphatic Filariasis in Kenya and its Role in the National Programmes for Elimination of Lymphatic Filariasis

We conducted a prospective; cross-sectional study to examine and compare treatment coverage of lymphatic filariasis by the health system (HST) and a health system implemented; community-directed treatment for the control of lymphatic filariasis (ComDT/HS) in 44 randomly selected villages in coastal Kenya. Demographic information on the villages and peripheral health facilities to guide design and implementation was obtained from a situation analysis phase of this study. A series of interactive training sessions on basic biology of lymphatic filariasis; concept and philosophy of ComDT/HS were given to members of the District Health Management Team (DHMT); peripheral health staff; community leaders and community drug distributors (CDDs) prior to ivermectin distribution. An intensive sensitization process of the community by the trained peripheral health staff and community leaders followed before selection of the CDDs. Quantitative and qualitative data for evaluation of the study were collected by coverage surveys of randomly selected households; focus group discussions and interviews; immediately after the drug distribution. Treatment coverage of all eligible persons was 46.5 and 88in HST and ComDT/HS villages; respectively; P 0.001. In comparing treatment coverage by the two study arms in relationship to the distance from a health facility; coverage among HST and not ComDT/HS villages was influenced by distance. In Kenya; ComDT/HS can effectively be implemented by the regular health system and can attain coverage levels compatible with the global filariasis elimination goal