Are local plague endemicity and ecological characteristics of vectors and reservoirs related? A case study in north-east Tanzania

The pattern of plague endemicity in Tanzania is characterized by continuous re-appearance of the disease in some locations, while in other neighbouring villages the disease has never or seldom been observed. To understand the reasons for this pattern, we studied small mammal and flea species composition, diversity and relative abundances in two plague-endemic and two plague-free locations. We asked （a） whether fleas more abundant in plague-endemic locations differ in their characteristic abundance and the degree of their host specificity from fleas more abundant in plague-free locations and （b） whether hosts most abundant in p/ague-endemic locations differ in the diversity of their flea assemblages from hosts most abundant in p/ague-free locations. We characterized （a） each host species by species richness and degree of taxonomic relatedness of its flea assemblages and （b） each flea species by its mean abundance and size, and degree of taxonomic relatedness of its host spectrum and compared their relative abundances between locations. No significant difference between plague-endemic and plague-free locations in either host density or any variable related to flea abundance or diversity was found. However, there was marginally significant effect of taxonomic distinctness of a flea assemblage barboured by a host on its probability to be more abundant in either plague-endemic or plague-free locations. Furthermore, hosts more abundant in plague-endemic locations tended to harbour closely-related fleas. Finally, while opportunistic and specialist fleas were equally distributed in both sets of locations, fleas exploiting distantly-related hosts were found mainly in plague-free locations during the rainy season. We suggest that the observed patterns might arise due to seasonal and spatial differences in local microclimatic conditions and landscape connectivity [ Current Zoology 55 （3） ： 200 - 211, 2009].

Human seroreactivity against Bartonella species in the Democratic Republic of Congo

Objective:To assess the presence and identity of Bartonella species in a pool of human blood samples from DRC Congo.Methods:Blood(±120μL) was collected anonymously from Congolese patients and placed on calibrated filter papers.Bartonella serology determination was performed using an indirect immun of luorescence assay(IFA) against six specific Bartonella antigens and Coxiella burnetii(C.burnetii) antigen.The end cut- of f value for Bartonella sp.was a titre greater than 1200.Results:None of the patients was positive for Bartonella elizabethae, Bartonella vinsonii subsp.vinsonii or Bartonella vinsonii subsp.arupensis nor for C.burnetti, but 4.5%of the 1SS samples were positive for either Bartonella henselae,Bartonella quintana, or Bartonella clarridgeiae.Conclusions:This preliminary study presents the first report of Bartonella species in the DR Congo and the first report of antibodies to Bartonella clarridgeiae in an African human population.Although few experimental trials have established the link between fleas and Bartonella transmission,the repeated detection of similar Bartonella species in fleas and humans in several countries suggests that Bartonellosis could be another flea-borne disease which specific reservoirs are still unknown.

High prevalence of epilepsy in onchocerciasis endemic health areas in Democratic Republic of the Congo

Background:A high prevalence of epilepsy has been observed in many onchocerciasis endemic regions.This study is to estimate the prevalence of active epilepsy and exposure to Onchocerca volvulus infection in a rural population in Ituri province,Democratic Republic of Congo.Methods:In August 2016,a community-based cross-sectional study was conducted in an onchocerciasis endemic area in the rural health zone of Logo,Ituri Province.Households within two neighbouring health areas were randomly sampled.To identify persons with epilepsy,a three-stage approach was used.In the first stage,all individuals of the selected households were screened for epilepsy by non-medical field workers using a validated 5-item questionnaire.In the second and third stage,suspected cases of epilepsy were examined by non-specialist medical doctors,and by a neurologist,respectively.A case of epilepsy was defined according to the 2014 International League Against Epilepsy(ILAE)guidelines.Exposure to O.volvulus was assessed by testing for IgG4 antibodies to an O.volvulus antigen(OV16 Rapid Test,)in individuals aged 3 years and older.Results:Out of 1389 participants included in the survey,64 were considered to have active epilepsy(prevalence 4.6%)(95%confidence interval[CI]:3.6-5.8).The highest age-specific epilepsy prevalence estimate was observed in those aged 20 to 29 years(8.2%).Median age of epilepsy onset was 10 years,with a peak incidence of epilepsy in the 10 to 15 year-old age group.OV16 test results were available for 912 participants,of whom 30.5%(95%CI,27.6-33.6)tested positive.The prevalence of OV16 positivity in a village ranged from 8.6 to 68.0%.After adjusting for age,gender and ivermectin use,a significant association between exposure to onchocerciasis and epilepsy was observed(adjusted odds ratio=3.19,95%CI:1.63-5.64)(P<0.001).Conclusions:A high prevalence of epilepsy and a significant association between epilepsy and exposure to O.volvulus were observed in the population in Ituri province,Democratic Republic of Congo.There is an urgent need to implement a CDTI programme and to scale up an epilepsy treatment and care programme.

Seasonal and habitat dependence of fleas parasitic on small mammals in Tanzania

We investigated host and flea species composition across different habitats during dry and rainy seasons in the Western Usambara Mountains in Tanzania.During both seasons,similarity in flea species composition increased with an increase in the similarity in host species composition.Nevertheless,between-season within-habitat as well as within-season between-habitat similarity in host species composition was higher than similarity in flea species composition.Ordination of habitats according to their host and flea species composition demonstrated that the pattern of between-habitat similarity in both host and flea species composition varied seasonally.Despite the relatively rich mammal and flea fauna of the study region,the major contribution to variation in species composition between seasons and among habitats was due to a few species only.Flea assemblages on Lophuromys kilonzoi Verheyen et al.,2007 and Praomys delectorum Thomas,1910 in different habitats were equally similar in either season.In contrast,flea assemblages on Mastomys natalensis(Smith,1834)occurring in different habitats were more similar in the dry than in the rainy season,whereas the opposite was the case for fleas on Grammomys sp.In different hosts,the main differences in species composition of flea assemblages between seasons as well as among habitats were due to different flea species.Although our results support the earlier idea that parasite species composition is determined by both host species composition and habitat properties,the former appears to explain variance in flea species composition between localities in the tropics better than between localities in temperate and arid zones.

Preliminary investigation on rodent–ectoparasite associations in the highlands of Tigray, Northern Ethiopia:implications for potential zoonoses

We studied associations between rodents and their arthropod ectoparasites in crop fields and household compounds in the highlands of Tigray,Northern Ethiopia.Ectoparasite infestation indices,such as percent infestation,mean abundance,prevalence and host preferences,were calculated for each taxon.In total,172 rodents from crop fields and 97 from household compounds were trapped.Rodent species and numbers trapped from the crop fields and household compounds were Mastomys awashensis(Lavrenchenko,Likhnova&Baskevich,1998)(88 and 44),Arvicanthis dembeensis(Ruppel,1842)(63 and 37)and Acomys sp.(21 and 16),respectively.A total of 558 insects and acarids(belonging to 11 taxa)were recovered from the rodents trapped in the crop fields,and 296 insects and acarid(belonging to 6 taxa)from the rodents trapped in the household compounds.Approximately 66%of the rodents trapped from the crop fields and 47%of those trapped from the household compounds were infested with ectoparasites.Laelaps sp.(64.9%)and Xenopsylla sp.(20.6%)comprised the highest proportion of the ectoparasites recovered in the crop fields,and the same ectoparasites,but in reverse order,comprised the highest proportions in the household compounds(Xenopsylla[50.3%]and Laelaps sp.[29%]).Our study revealed that crop fields and household compounds in the highlands share similar rodents and several ectoparasites.Furthermore,at least 1 of the rodent species and some of the ectoparasites identified in this study were reported to have posed medical and veterinary threats in other parts of Ethiopia and neighboring countries.

Onchocerca volvulus as a risk factor for developing epilepsy in onchocerciasis endemic regions in the Democratic Republic of Congo:a case control study

Background:A high prevalence of epilepsy has been observed in onchocerciasis endemic areas in the Democratic Republic of Congo(DRC).With this study we aimed to investigate whether Onchocerca volvulus infection is a risk factor for developing epilepsy in onchocerciasis endemic regions in the DRC.Methods:Between October and December 2015,a multi-centre case control study was performed in onchocerciasis endemic health zones(HZ)in the DRC:one study site was situated in Tshopo Province in the HZ of Wanierukula(village of Salambongo)where there had been 13 annual community distributions of treatment with ivermectin(CDTI),a second was situated in Ituri Province in the HZ of Logo(village of Draju)where ivermectin had never been distributed and in the HZ of Rethy(village of Rassia)where there had been THREE CDTI annual campaigns before the study.Individuals with unprovoked convulsive epilepsy of unknown etiology were enrolled as cases(n=175).Randomly selected healthy members of families without epilepsy cases from the same village and age-groups and were recruited as controls(n=170).Results:Onchocerciasis associated symptoms(e.g.,itching and abnormal skin)were more often present in cases compared to controls(respectively,OR=2.63,95%CI:1.63-4.23,P<0.0001 and OR=3.23,95%CI:1.48-7.09,P=0.0034).A higher number of cases was found to present with microfilariae in skin snips and with O.volvulus IgG4 antibodies in the blood compared to controls.Moreover,the microfilariae load in skin snips was 3-10 times higher in cases than controls.Conclusions:This case control study confirms that O.volvulus is a risk factor for developing epilepsy in onchocerciasis endemic regions in the DRC.