Survey of aquatic bugs' species in Bankim, a new endemic area in Cameroon

Bankim district located in the Northern part of Cameroon (Adamaoua region: N 06°04\u2705" E 10°27\u2737"), has been recently described as a new endemic site in Cameroon. This region benefited from the construction of a dam which considerably modified the environment. Previous collections of some aquatic bugs in this region were shown positive for M. ulcerans. But aquatic bugs’ biodiversity and biology still poorly documented. In the afore-mentioned context the present study was carried out to identify the commonly occurring medium and large size aquatic bugs fauna and workout their relative abundance, diversity  according to type of water bodies and comparing with those trap in the night by light trap.  Insects were collected daily from June 1st to June 30 2010 in ponds formed around dam flooded area, in streams and a river. Light traps made up of a 250 W bulb connected to an electrical generator put in front of a white sheet, were installed from 6 PM to 11PM during one lunar cycle, in 3 sites (near the dam, near habitations and in the forest) in the same month.  We collected 338 aquatic bugs in different water bodies belonging to 6 families. Belostomatidae was numerically the most abundant group constituting of 33.13 % of the total aquatic insects followed by Naucoridae, Ranatridae (27.81%, 18.63%).  The other families identified were Nepidae, Notonectidae, and of Gerridae representing respectively 9.46%, 5.91% and 5.02%. All families identified were present in streams and ponds but only two families (Ranatridae and Nepidae) were collected in the river;  Among these 338 aquatic bugs, 59.17% (200) were collected in the streams, 38.16% (129) in the ponds and only 9 (2.66%) in the river. Through the light trap only 2 families were identified among a total of 390 aquatic bugs caught. Belostomatidae , predominant with 80.51% and Notonectidae 19.49%. Notonectidae were caught all along the month and during the full moon, but Belostomatidae were absent during full moon. According to the site of collection, we obtained 25.64% (100) of Belostomatidae and 11.94% (46) of Notonectidae near the dam; near habitations 21.53% (84) of Belostomatidae and 2.56% (10) of Notonectidae and in the forest, 33.33% (130) of Belostomatidae and 5.12% (20) of Notonectidae. This preliminary entomological survey shows the variation of aquatic bugs\u27 diversity according to the types of water bodies in the same endemic region and according to light attraction and the moon phases.

Troisième cours international portant sur la microbiologie de M. ulcerans (M2U) à Yaoundé

International audienc

A field study in Benin to investigate the role of mosquitoes and other flying insects in the ecology of Mycobacterium ulcerans

Background Buruli ulcer, the third mycobacterial disease after tuberculosis and leprosy, is caused by the environmental mycobacterium M. ulcerans. There is at present no clear understanding of the exact mode(s) of transmission of M. ulcerans. Populations affected by Buruli ulcer are those living close to humid and swampy zones. The disease is associated with the creation or the extension of swampy areas, such as construction of dams or lakes for the development of agriculture. Currently, it is supposed that insects (water bugs and mosquitoes) are host and vector of M. ulcerans. The role of water bugs was clearly demonstrated by several experimental and environmental studies. However, no definitive conclusion can yet be drawn concerning the precise importance of this route of transmission. Concerning the mosquitoes, DNA was detected only in mosquitoes collected in Australia, and their role as host/vector was never studied by experimental approaches. Surprisingly, no specific study was conducted in Africa. In this context, the objective of this study was to investigate the role of mosquitoes (larvae and adults) and other flying insects in ecology of M. ulcerans. This study was conducted in a highly endemic area of Benin. Methodology/Principal Findings Mosquitoes (adults and larvae) were collected over one year, in Buruli ulcer endemic in Benin. In parallel, to monitor the presence of M. ulcerans in environment, aquatic insects were sampled. QPCR was used to detected M. ulcerans DNA. DNA of M. ulcerans was detected in around 8.7% of aquatic insects but never in mosquitoes (larvae or adults) or in other flying insects. Conclusion/Significance This study suggested that the mosquitoes don't play a pivotal role in the ecology and transmission of M. ulcerans in the studied endemic areas. However, the role of mosquitoes cannot be excluded and, we can reasonably suppose that several routes of transmission of M. ulcerans are possible through the world

Spatio-temporal patterns and landscape-associated risk of Buruli ulcer in Akonolinga, Cameroon

Background: Buruli ulcer (BU) is an extensively damaging skin infection caused by Mycobacterium ulcerans, whose transmission mode is still unknown. The focal distribution of BU and the absence of interpersonal transmission suggest a major role of environmental factors, which remain unidentified. This study provides the first description of the spatio-temporal variations of BU in an endemic African region, in Akonolinga, Cameroon. We quantify landscape-associated risk of BU, and reveal local patterns of endemicity. Methodology/Principal Findings: From January 2002 to May 2012, 787 new BU cases were recorded in 154 villages of the district of Akonolinga. Incidence per village ranged from 0 (n = 59 villages) to 10.4 cases/1000 person. years (py); median incidence was 0.4 cases/1,000py. Villages neighbouring the Nyong River flood plain near Akonolinga town were identified as the highest risk zone using the SPODT algorithm. We found a decreasing risk with increasing distance to the Nyong and identified 4 time phases with changes in spatial distribution. We classified the villages into 8 groups according to landscape characteristics using principal component analysis and hierarchical clustering. We estimated the incidence ratio (IR) associated with each landscape using a generalised linear model. BU risk was highest in landscapes with abundant wetlands, especially cultivated ones (IR = 15.7, 95% confidence interval [95% CI] = 15.7[4.2-59.2]), and lowest in reference landscape where primary and secondary forest cover was abundant. In intermediate-risk landscapes, risk decreased with agriculture pressure (from IR[95% CI] = 7.9[2.2-28.8] to 2.0[0.6-6.6]). We identified landscapes where endemicity was stable and landscapes where incidence increased with time. Conclusion/Significance: Our study on the largest series of BU cases recorded in a single endemic region illustrates the local evolution of BU and identifies the Nyong River as the major driver of BU incidence. Local differences along the river are explained by wetland abundance and human modification of the environment

The "Buruli Score": development of a multivariable prediction model for diagnosis of Mycobacterium ulcerans infection in individuals with ulcerative skin lesions, Akonolinga, Cameroon

Background Access to laboratory diagnosis can be a challenge for individuals suspected of Buruli Ulcer (BU). Our objective was to develop a clinical score to assist clinicians working in resource- limited settings for BU diagnosis. Methododology/Principal Findings Between 2011 and 2013, individuals presenting at Akonolinga District Hospital, Cameroon, were enrolled consecutively. Clinical data were collected prospectively. Based on a latent class model using laboratory test results (ZN, PCR, culture), patients were categorized into high, or low BU likelihood. Variables associated with a high BU likelihood in a multivariate logistic model were included in the Buruli score. Score cut-offs were chosen based on calculated predictive values. Of 325 patients with an ulcerative lesion, 51 (15.7%) had a high BU likelihood. The variables identified for the Buruli score were: characteristic smell (+3 points), yellow color (+2), female gender (+2), undermining (+1), green color (+1), lesion hyposensitivity (+1), pain at rest (-1), size >5cm (-1), locoregional adenopathy (-2), age above 20 up to 40 years (-3), or above 40 (-5). This score had AUC of 0.86 (95% CI 0.82-0.89), indicating good discrimination between infected and non-infected individuals. The cut-off to reasonably exclude BU was set at scores = 4 (PPV 69.0%; 95% CI 49.2-84.7). Patients with intermediate BU probability needed to be tested by PCR. Conclusions/Significance We developed a decisional algorithm based on a clinical score assessing BU probability. The Buruli score still requires further validation before it can be recommended for wide use

Mycobacterium ulcerans ecological dynamics and its association with freshwater ecosystems and aquatic communities : results from a 12-month environmental survey in Cameroon

Background: Mycobacterium ulcerans (MU) is the agent responsible for Buruli Ulcer (BU), an emerging skin disease with dramatic socioeconomic and health outcomes, especially in rural settings. BU emergence and distribution is linked to aquatic ecosystems in tropical and subtropical countries, especially to swampy and flooded areas. Aquatic animal organisms are likely to play a role either as host reservoirs or vectors of the bacilli. However, information on MU ecological dynamics, both in space and time, is dramatically lacking. As a result, the ecology of the disease agent, and consequently its mode of transmission, remains largely unknown, which jeopardizes public health attempts for its control. The objective of this study was to gain insight on MU environmental distribution and colonization of aquatic organisms through time. Methodology/Principal Findings: Longitudinal sampling of 32 communities of aquatic macro-invertebrates and vertebrates was conducted from different environments in two BU endemic regions in Cameroon during 12 months. As a result, 238,496 individuals were classified and MU presence was assessed by qPCR in 3,084 sample-pools containing these aquatic organisms. Our study showed a broad distribution of MU in all ecosystems and taxonomic groups, with important regional differences in its occurrence. Colonization dynamics fluctuated along the year, with the highest peaks in August and October. The large variations observed in the colonization dynamics of different taxonomic groups and aquatic ecosystems suggest that the trends shown here are the result of complex ecological processes that need further investigation. Conclusion/Perspectives: This is the largest field study on MU ecology to date, providing the first detailed description of its spatio-temporal dynamics in different aquatic ecosystems within BU endemic regions. We argue that coupling this data with fine-scale epidemiological data through statistical and mathematical models will provide a major step forward in the understanding of MU ecology and mode of transmission

Biodiversity of water bugs in Cameroon

Date du colloque&nbsp;: 04/2008</p

The Guinea-Bissau Family of Mycobacterium tuberculosis Complex Revisited

The Guinea-Bissau family of strains is a unique group of the Mycobacterium tuberculosis complex that, although genotypically closely related, phenotypically demonstrates considerable heterogeneity. We have investigated 414 M. tuberculosis complex strains collected in Guinea-Bissau between 1989 and 2008 in order to further characterize the Guinea-Bissau family of strains. To determine the strain lineages present in the study sample, binary outcomes of spoligotyping were compared with spoligotypes existing in the international database SITVIT2. The major circulating M. tuberculosis clades ranked in the following order: AFRI (n = 195, 47.10%), Latin-American-Mediterranean (LAM) (n = 75, 18.12%), ill-defined T clade (n = 53, 12.8%), Haarlem (n = 37, 8.85%), East-African-Indian (EAI) (n = 25, 6.04%), Unknown (n = 12, 2.87%), Beijing (n = 7, 1.68%), X clade (n = 4, 0.96%), Manu (n = 4, 0.97%), CAS (n = 2, 0.48%). Two strains of the LAM clade isolated in 2007 belonged to the Cameroon family (SIT61). All AFRI isolates except one belonged to the Guinea-Bissau family, i.e. they have an AFRI_1 spoligotype pattern, they have a distinct RFLP pattern with low numbers of IS6110 insertions, and they lack the regions of difference RD7, RD8, RD9 and RD10, RD701 and RD702. This profile classifies the Guinea-Bissau family, irrespective of phenotypic biovar, as part of the M. africanum West African 2 lineage, or the AFRI_1 sublineage according to the spoligtyping nomenclature. Guinea-Bissau family strains display a variation of biochemical traits classically used to differentiate M. tuberculosis from M. bovis. Yet, the differential expression of these biochemical traits was not related to any genes so far investigated (narGHJI and pncA). Guinea-Bissau has the highest prevalence of M. africanum recorded in the African continent, and the Guinea-Bissau family shows a high phylogeographical specificity for Western Africa, with Guinea-Bissau being the epicenter. Trends over time however indicate that this family of strains is waning in most parts of Western Africa, including Guinea-Bissau (p = 0.048)

Fine needle aspiration for the diagnosis of M. ulcerans infection and for mycolactone detection

Over recent years, management of Buruli ulcer patients has considerably changed with advances in antibiotherapy. Antibiotherapy is particularly effective on nonulcerative forms. However, the bacteriological diagnosis in the early forms is difficult because simple and non-invasive methods are not available. In this study, the diagnostic effectiveness of the Fine Needle aspiration was evaluated on early lesions. Our results showed that PCR from FNA samples, unlike Ziehl-Neelsen staining, is very sensitive on nonulcerative forms like other standard sampling methods (biopsy and punch biopsy). Furthermore, mycolactone was detected in aspirated liquid from lesions in mouse experimentally infected by M. ulcerans and in FNA from Buruli ulcer patients. This is a crucial observation to encourage the development of diagnosis test based on mycolactone detection. Moreover, mycolactone was never detected in aspirated liquid from a patient treated by antibiotherapy. To conclude, fine needle aspiration is a simple, fast, painless, accurate and inexpensive method of sampling and could be used for diagnosis of M. ulcerans infection

A Molecular Epidemiological and Genetic Diversity Study of Tuberculosis in Ibadan, Nnewi and Abuja, Nigeria

Background Nigeria has the tenth highest burden of tuberculosis (TB) among the 22 TB high-burden countries in the world. This study describes the biodiversity and epidemiology of drug-susceptible and drug-resistant TB in Ibadan, Nnewi and Abuja, using 409 DNAs extracted from culture positive TB isolates. Methodology/Principal Findings DNAs extracted from clinical isolates of Mycobacterium tuberculosis complex were studied by spoligotyping and 24 VNTR typing. The Cameroon clade (CAM) was predominant followed by the M. africanum (West African 1) and T (mainly T2) clades. By using a smooth definition of clusters, 32 likely epi-linked clusters related to the Cameroon genotype family and 15 likely epi-linked clusters related to other “modern” genotypes were detected. Eight clusters concerned M. africanum West African 1. The recent transmission rate of TB was 38%. This large study shows that the recent transmission of TB in Nigeria is high, without major regional differences, with MDR-TB clusters. Improvement in the TB control programme is imperative to address the TB control problem in Nigeria