Bovine Tuberculosis Prevalence Survey on Cattle in the Rural Livestock System of Torodi (Niger)

BACKGROUND: Bovine tuberculosis (BTB) is a widespread zoonosis in developing countries but has received little attention in sub-Saharan Africa, especially in Niger. Recent investigations confirmed the high incidence of the disease in cattle slaughtered in an abattoir in Niamey. The fact that most of the animals in which M. bovis has been identified were from the rural area of Torodi implied the existence of a probable source of BTB in this region. This study aimed to determine the prevalence of BTB infection in cattle and to identify risk factors for infection in human and cattle populations in Torodi. METHODS AND PRINCIPAL FINDINGS: A survey was carried out at the level of households keeping livestock (n = 51). The questionnaire was related to the potential risk factors and the presence of clinical signs of TB both in animals and humans. Comparative Intradermal Tuberculin Test was conducted to determine the TB status in cattle (n = 393). The overall apparent individual animal prevalence of tuberculin reactors was 3.6% (CI: 95%, 1.9-5.9), whereas the individual true prevalence was estimated at 0.8% (CI: 95%, 0.0-5.0). Using a multivariate logistic regression analysis and a classification tree analysis, the only household level risk factor that significantly influenced the presence of BTB in cattle was the presence of animals coughing in the herd (OR = 4.7, 95% CI: 1.12-19.71, p-value = 0.034). The lack of the practice of quarantine was borderline significant (OR = 4.2, 95% CI: 0.96-18.40, p-value = 0.056). CONCLUSION/SIGNIFICANCE: The study confirmed that BTB is endemic in cattle in Torodi and the risk of the transmission of the disease to humans is potentially high. For the control of the disease in livestock, slaughtering of infected animals and the compensation of the owners is needed. Collaboration between the veterinary and the medical sectors, in the diagnosis, monitoring, prevention and control of BTB is strongly encouraged

Highly Pathogenic Avian Influenza Virus Subtype H5N1 in Africa: A Comprehensive Phylogenetic Analysis and Molecular Characterization of Isolates

Highly pathogenic avian influenza virus A/H5N1 was first officially reported in Africa in early 2006. Since the first outbreak in Nigeria, this virus spread rapidly to other African countries. From its emergence to early 2008, 11 African countries experienced A/H5N1 outbreaks in poultry and human cases were also reported in three of these countries. At present, little is known of the epidemiology and molecular evolution of A/H5N1 viruses in Africa. We have generated 494 full gene sequences from 67 African isolates and applied molecular analysis tools to a total of 1,152 A/H5N1 sequences obtained from viruses isolated in Africa, Europe and the Middle East between 2006 and early 2008. Detailed phylogenetic analyses of the 8 gene viral segments confirmed that 3 distinct sublineages were introduced, which have persisted and spread across the continent over this 2-year period. Additionally, our molecular epidemiological studies highlighted the association between genetic clustering and area of origin in a majority of cases. Molecular signatures unique to strains isolated in selected areas also gave us a clearer picture of the spread of A/H5N1 viruses across the continent. Mutations described as typical of human influenza viruses in the genes coding for internal proteins or associated with host adaptation and increased resistance to antiviral drugs have also been detected in the genes coding for transmembrane proteins. These findings raise concern for the possible human health risk presented by viruses with these genetic properties and highlight the need for increased efforts to monitor the evolution of A/H5N1 viruses across the African continent. They further stress how imperative it is to implement sustainable control strategies to improve animal and public health at a global level

Univariate analysis of raw data indicating potential risk factors associated with bovine tuberculosis (BTB) in cattle and humans in the rural area of Torodi, Niger.

<p>*These values had <i>P</i>-value<0.25 and were identified as potential risk factors for inclusion in the multivariable analysis; Ref: indicate that the level is taken as the reference to which others are compared; ND: not determined;</p><p>**Target variable for multivariate analysis and CART analysis.</p

Location of the study zone (Torodi) in Niger.

<p>Location of the study zone (Torodi) in Niger.</p

Apparent prevalence in local cattle (n = 393) in the rural zone of Torodi, Niger.

<p>Apparent prevalence (AP) and estimation of the true prevalence (TP) of bovine tuberculosis among local cattle (n = 393) in the rural zone of Torodi, Niger. TP was calculated using the value of Sensitivity and Specificity for the cut-off of >4 mm according to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0024629#pone.0024629-Alambedji1" target="_blank">[8]</a>.</p

Within herd apparent prevalence in local cattle (n = 393) in the rural zone of Torodi, Niger.

<p>Apparent prevalence (AP) and estimation of the true prevalence (TP) of bovine tuberculosis among local cattle (n = 393) in the rural zone of Torodi, Niger. TP was calculated using the value of Sensitivity and Specificity for the cut-off of >4 mm according to Ameni et al. (2008).</p><p>*Number of households in which animals were tested by comparative intra-dermal tuberculin testing (CITT).</p

Ranking of BTB risk factors by overall discriminatory power using CART.

<p>Ranking of BTB risk factors by overall discriminatory power using CART.</p

Results of the final multivariable logistic regression model using backward stepwise selection with significant household level risk factors for bovine tuberculosis in the Torodi zone of Niger.

<p>Ref: indicate that the level is taken as the reference to which others are compared;</p><p>*: quarantine was practiced;</p><p>**: mixed newly arrivals animals.</p

Classification tree produced using CART with target variable “CITT” (1 having at least one animal tested positive by CITT within the household; 0: not having animals tested positive by CITT within the household).

<p>Classification tree representing the important factors influencing CITT positivity. Target variable is “CITT” (1 having at least one animal tested positive by CITT within the household; 0: not having animals tested positive by CITT within the household). The following variables were selected by the tree as important factors: herd size with a cut off of 19 cattle in the herd; Handling (quarantine: keeping newly arrived animals out of the herd – mixed: new animals mixed with the other animals); Animals chronic cough (0 = absence of animals with chronic cough in the herd and 1 = presence of animals with chronic cough).</p

Highly pathogenic avian influenza virus subtype H5N1 in Africa: a comprehensive phylogenetic analysis and molecular characterization of isolates.

Highly pathogenic avian influenza virus A/H5N1 was first officially reported in Africa in early 2006. Since the first outbreak in Nigeria, this virus spread rapidly to other African countries. From its emergence to early 2008, 11 African countries experienced A/H5N1 outbreaks in poultry and human cases were also reported in three of these countries. At present, little is known of the epidemiology and molecular evolution of A/H5N1 viruses in Africa. We have generated 494 full gene sequences from 67 African isolates and applied molecular analysis tools to a total of 1,152 A/H5N1 sequences obtained from viruses isolated in Africa, Europe and the Middle East between 2006 and early 2008. Detailed phylogenetic analyses of the 8 gene viral segments confirmed that 3 distinct sublineages were introduced, which have persisted and spread across the continent over this 2-year period. Additionally, our molecular epidemiological studies highlighted the association between genetic clustering and area of origin in a majority of cases. Molecular signatures unique to strains isolated in selected areas also gave us a clearer picture of the spread of A/H5N1 viruses across the continent. Mutations described as typical of human influenza viruses in the genes coding for internal proteins or associated with host adaptation and increased resistance to antiviral drugs have also been detected in the genes coding for transmembrane proteins. These findings raise concern for the possible human health risk presented by viruses with these genetic properties and highlight the need for increased efforts to monitor the evolution of A/H5N1 viruses across the African continent. They further stress how imperative it is to implement sustainable control strategies to improve animal and public health at a global level