Genetic variation in the immune system and malaria susceptibility in infants: a nested case-control study in Nanoro, Burkina Faso

BACKGROUND

Genetic polymorphisms in the human immune system modulate susceptibility to malaria. However, there is a paucity of data on the contribution of immunogenetic variants to malaria susceptibility in infants, who present differential biological features related to the immaturity of their adaptive immune system, the protective effect of maternal antibodies and fetal haemoglobin. This study investigated the association between genetic variation in innate immune response genes and malaria susceptibility during the first year of life in 656 infants from a birth cohort survey performed in Nanoro, Burkina Faso.

METHODS

Seventeen single nucleotide polymorphisms (SNPs) in 11 genes of the immune system previously associated with different malaria phenotypes were genotyped using TaqMan allelic hybridization assays in a Fluidigm platform. Plasmodium falciparum infection and clinical disease were documented by active and passive case detection. Case-control association analyses for both alleles and genotypes were carried out using univariate and multivariate logistic regression. For cytokines showing significant SNP associations in multivariate analyses, cord blood supernatant concentrations were measured by quantitative suspension array technology (Luminex).

RESULTS

Genetic variants in IL-1β (rs1143634) and FcγRIIA/CD32 (rs1801274)-both in allelic, dominant and co-dominant models-were significantly associated with protection from both P. falciparum infection and clinical malaria. Furthermore, heterozygote individuals with rs1801274 SNP in FcγRIIA/CD32 showed higher IL-1RA levels compared to wild-type homozygotes (P = 0.024), a cytokine whose production is promoted by the binding of IgG immune complexes to Fcγ receptors on effector immune cells.

CONCLUSIONS

These findings indicate that genetic polymorphisms in genes driving innate immune responses are associated to malaria susceptibility during the first year of life, possibly by modulating production of inflammatory mediators.

Bayesian Evaluation of Three Serological Tests for Detecting Antibodies against Brucella spp. among Humans in the Northwestern Part of Ecuador

Brucellosis is an important but neglected zoonosis that causes serious economic losses both in livestock and human populations. The aim of the present study was to estimate the true prevalence of brucellosis together with diagnostic sensitivity and specificity of three serological tests in humans of the northwestern part of Ecuador using a Bayesian approach adjusted for the dependencies among the multiple tests to avoid any misinterpretation. In addition, the causal agent responsible for human brucellosis was also identified. Using a total of 3,733 samples collected from humans in this area between 2006 and 2008, the prevalence of human brucellosis and the diagnostic test characteristics of the Rose Bengal fast agglutination test (RBT), Wright's slow agglutination test with ethylenediaminetetraacetic acid disodium salt dehydrate (EDTA) (SAT-EDTA), and indirect ELISA (iELISA) were estimated using a Bayesian approach. The estimated true prevalence of human brucellosis was 1% (credibility interval: 0.4-1.6). The sensitivities of iELISA and RBT were higher than and similar (95.1% and 95.0%, respectively) to those of SAT-EDTA (60.8%). Even though all tests indicated a high specificity (> 99.0%), the specificity of SAT-EDTA was highest (99.9%). The circulating strain in this study area was identified to be Brucella abortus biotype 4 based on culture and microbiological characterization. The RBT and the iELISA are recommended for estimating the true prevalence of human brucellosis and/or for surveillance programs following their high sensitivities and specificities. The proposed strategy supports evidence-based medicine for clinicians and policy-makers to ensure appropriate preventive and control program of brucellosis worldwide.

Effects of 'The Vicious Worm' educational tool on Taenia solium knowledge retention in Zambian primary school students after one year

BACKGROUND

Taenia solium is a neglected zoonotic parasite endemic throughout many low-income countries worldwide, including Zambia, where it causes human and pig diseases with high health and socioeconomic burdens. Lack of knowledge is a recognized risk factor, and consequently targeted health educational programs can decrease parasite transmission and disease occurrence in endemic areas. Preliminary assessment of the computer-based education program 'The Vicious Worm' in rural areas of eastern Zambia indicated that it was effective at increasing knowledge of T. solium in primary school students. The aim of this study was to evaluate the impact of 'The Vicious Worm' on knowledge retention by re-assessing the same primary school students one year after the initial education workshops.

METHODOLOGY/PRINCIPAL FINDINGS

Follow-up questionnaires were administered in the original three primary schools in eastern Zambia in 2017, 12 months after the original workshops. In total, 86 pupils participated in the follow-up sessions, representing 87% of the initial workshop respondents. Knowledge of T. solium at 'follow-up' was significantly higher than at the initial 'pre' questionnaire administered during the Vicious Worm workshop that took place one year earlier. While some specifics of the parasite's life cycle were not completely understood, the key messages for disease prevention, such as the importance of hand washing and properly cooking pork, remained well understood by the students, even one year later.

CONCLUSIONS/SIGNIFICANCE

Results of this study indicate that 'The Vicious Worm' may be an effective tool for both short- and long-term T. solium education of rural primary school students in Zambia. Inclusion of educational workshops using 'The Vicious Worm' could be recommended for integrated cysticercosis control/elimination programs in sub-Saharan Africa, particularly if the content is simplified to focus on the key messages for prevention of disease transmission.

Dispersal capacity of Haematopota spp. and Stomoxys calcitrans using a mark-release-recapture approach in Belgium

The dispersion potential of mechanical vectors is an important factor in the dissemination of pathogens. A mark-release-recapture experiment was implemented using two groups (unfed and partially fed) of the Tabanidae (Diptera) (Haematopota spp.) and biting Muscidae (Diptera) (Stomoxys calcitrans) most frequently collected in Belgium in order to evaluate their dispersion potential. In total, 2104 specimens of Haematopota spp. were collected directly from horses and 5396 S. calcitrans were collected in a cattle farm using hand-nets. Some of these insects were partially fed in vitro and all were subsequently coloured. Overall, 67 specimens of S. calcitrans (1.2%) and 17 of Haematopota spp. (0.8%) were recaptured directly on horses. Stomoxys calcitrans flew maximum distances of 150 m and 300 m when partially fed and unfed, respectively. Haematopota spp. travelled maximum distances of 100 m and 200 m when partially fed and unfed, respectively. Segregation measures seem essential in order to reduce the risk for pathogen transmission. A distance of 150 m appears to be the minimum required for segregation to avoid the risk for mechanical transmission, but in areas of higher vector density, this should probably be increased.

Estimating prevalence and diagnostic test characteristics of bovine cysticercosis in Belgium in the absence of a 'gold standard' reference test using a Bayesian approach

A Bayesian model was developed to estimate values for the prevalence and diagnostic test characteristics of bovine cysticercosis (Taenia saginata) by combining results of four imperfect tests. Samples of 612 bovine carcases that were found negative for cysticercosis during routine meat inspection collected at three Belgian slaughterhouses, underwent enhanced meat inspection (additional incisions in the heart), dissection of the predilection sites, B158/B60 Ag-ELISA and ES Ab-ELISA. This Bayesian approach allows for the combination of prior expert opinion with experimental data to estimate the true prevalence of bovine cysticercosis in the absence of a gold standard test. A first model (based on a multinomial distribution and including all possible interactions between the individual tests) required estimation of 31 parameters, while only allowing for 15 parameters to be estimated. Including prior expert information about specificity and sensitivity resulted in an optimal model with a reduction of the number of parameters to be estimated to 8. The estimated bovine cysticercosis prevalence was 33.9% (95% credibility interval: 27.7-44.4%), while apparent prevalence based on meat inspection is only 0.23%. The test performances were estimated as follows (sensitivity (Se) - specificity (Sp)): enhanced meat inspection (Se 2.87% - Sp 100%), dissection of predilection sites (Se 69.8% - Sp 100%), Ag-ELISA (Se 26.9% - Sp 99.4%), Ab-ELISA (Se 13.8% - Sp 92.9%).

Survey of Anaplasma phagocytophilum and Anaplasma sp. 'Omatjenne' infection in cattle in Africa with special reference to Ethiopia

Background

As evidence of the infection of domestic animals by Anaplasma phagocytophilum and Anaplasma sp. ‘Omatjenne’ is presently becoming available, understanding the epidemiological and ecological significance of infection is important to quantify the clinical and socio-economic impact of the diseases they cause.

Methods

The first aim of this study was to analyse the occurrence of A. phagocytophilum and Anaplasma sp. ‘Omatjenne’ in cattle samples collected from selected African countries using a polymerase chain reaction and restriction enzyme fragment length polymorphism. Secondly, this study was aimed at the molecular identification of Ehrlichia spp. and Anaplasma spp. infection in ruminants raised under different production systems in selected sites in central Ethiopia.

Results

In total, 695 samples from cattle in six African countries were analysed. Overall, 45 positive results were obtained for Anaplasma sp. ‘Omatjenne’ (6.47%) and 19 for A. phagocytophilum (2.73%). Anaplasma sp. ‘Omatjenne’ was detected in all countries except Tanzania while A. phagocytophilum was detected only in samples from Ethiopia. The proportion of samples tested positive for Anaplasma sp. ‘Omatjenne’ ranged from 1.2% in Morocco to 16% in Rwanda. The occurrence of both agents is now confirmed in African cattle. For the survey in Ethiopia a semi-nested 16S rDNA polymerase chain reaction followed by restriction fragment length polymorphism was used for the identification of Ehrlichia spp. and Anaplasma spp. in blood samples. Randomly selected samples were also analysed by pCS20 polymerase chain reaction for the detection of E. ruminantium. Positive results were obtained for E. ruminantium and five species of Anaplasma including a zoonotic species. To our knowledge, this is the first report of infection of domestic ruminants with A. phagocytophilum, A. ovis and Anaplasma sp. ‘Omatjenne’ in Ethiopia.

Conclusion

The present study showed widespread occurrence of Anaplasma sp. 'Omatijenne' in African cattle and five Anaplasma species in Ethiopia.

Preliminary assessment of the computer-based Taenia solium educational program 'The Vicious Worm' on knowledge uptake in primary school students in rural areas in eastern Zambia

OBJECTIVE

The zoonotic helminth Taenia solium is endemic in Zambia, causing human (taeniasis and (neuro)cysticercosis) and pig (porcine cysticercosis) diseases with high health, social and economic burdens. We aimed to evaluate the impact of a health educational program intended to lead to powerful and cumulative improvements in knowledge, attitudes and practices that decrease parasite transmission and disease occurrence.

METHODS

Half-day health education workshops were conducted in three primary schools in the highly endemic Eastern Province of Zambia, using the computer-based T. solium educational program 'The Vicious Worm'. Questionnaires were administered before and after the educational component to determine the program's impact on knowledge uptake in primary school students.

RESULTS

In total, 99 students participated: 38 males and 61 females, with a median age of 14 years (range 10-18 years). Baseline general knowledge of T. solium, including awareness of the different human and pig disease states, and disease diagnosis, treatment and prevention, was quite high (average score 62%) and consistent across all three study areas. Participants' knowledge had significantly increased after the educational component, particularly regarding parasite transmission and disease prevention.

CONCLUSION

Preliminary assessment of 'The Vicious Worm' indicates it is an effective tool for the short-term T. solium education of primary school students in Zambia. Follow-up studies are planned to assess the longer term impact of the program on knowledge uptake in the study neighbourhoods. Inclusion of tailored 'The Vicious Worm' educational workshops should be considered in integrated cysticercosis control programs in endemic areas of sub-Saharan Africa.

Taenia solium from a community perspective: Preliminary costing data in the Katete and Sinda districts in Eastern Zambia

The tapeworm Taenia solium is endemic in Zambia, however its socioeconomic cost is unknown. During a large-scale interventional study conducted in Zambia, baseline economic costs of human and porcine T. solium infections were measured. Questionnaire surveys were conducted within three neighbourhoods in Zambia's Eastern province in 2015 and 2016. A human health questionnaire, capturing costs of clinical symptoms commonly attributable to human cysticercosis and taeniasis, was conducted in randomly selected households (n = 267). All pig-keeping households were administered a pig socioeconomic questionnaire (n = 271) that captured pig demographic data, costs of pig-keeping, and economic losses from porcine cysticercosis. Of all respondents 62% had reportedly experienced at least one of the surveyed symptoms. Seizure-like episodes were reported by 12%, severe chronic headaches by 36%, and vision problems by 23% of respondents. These complaints resulted in 147 health care consultations and 17 hospitalizations in the five years preceding the study, and an estimated productivity loss of 608 working days per year. Of all pigs 69% were bought within villages. Nearly all adult pigs were sold to local traders, and tongue palpation for detection of cysticerci was commonly performed. Reportedly, 95% of pig owners could not sell tongue-positive pigs, while infected pigs fetched only 45% of the normal sale value. These preliminary costing data indicate that human and porcine T. solium infections substantially impact endemic areas of Eastern Zambia. A full socioeconomic burden assessment may enable improved T. solium management in sub-Saharan Africa.

Re-visiting the detection of porcine cysticercosis based on full carcass dissections of naturally Taenia solium infected pigs

Background

Taenia solium is a neglected zoonotic parasite. The performances of existing tools for the diagnosis of porcine cysticercosis need further assessment, and their shortcomings call for alternatives. The objective of this study was to evaluate the performance of tongue palpation and circulating antigen detection for the detection of porcine cysticercosis in naturally infected pigs of slaughter age compared to full carcass dissections (considered the gold standard). Additionally, alternative postmortem dissection procedures were investigated. A total of 68 rural pigs of slaughter age randomly selected in the Eastern Province of Zambia were dissected. Dissections were conducted on full carcasses (or half carcass in case cysticerci were already detected in the first half), including all the organs. Total cysticercus counts, location and stages were recorded and collected cysticerci were identified morphologically and molecularly. All sera were analysed with the B158/B60 antigen detecting ELISA (Ag-ELISA).

Results

Key findings were the high occurrence of T. solium infected pigs (56%) and the presence of T. solium cysticerci in the livers of 26% of infected animals. More than half of the infected carcasses contained viable cysticerci. Seven carcasses had T. hydatigena cysticerci (10%), out of which five carcasses were co-infected with T. hydatigena and T. solium; two carcasses (3%) had only T. hydatigena cysticerci. Compared to full carcass dissection, the specificity of the Ag-ELISA to detect infected carcasses was estimated at 67%, the sensitivity at 68%, increasing to 90% and 100% for the detection of carcasses with one or more viable cysticerci, and more than 10 viable cysts, respectively. Tongue palpation only detected 10% of the cases, half carcass dissection 84%.

Selective dissection of the diaphragm, tongue and heart or masseters can be considered, with an estimated sensitivity of 71%, increasing to 86% in carcasses with more than 10 cysticerci.

Conclusions

Depending on the aim of the diagnosis, a combination of Ag-ELISA and selective dissection, including investigating the presence of T. hydatigena, can be considered. Full carcass dissection should include the dissection of the liver, kidneys, spleen and lungs, and results should be interpreted carefully, as small cysticerci can easily be overlooked.

High prevalence of bovine cysticercosis found during evaluation of different post-mortem detection techniques in Belgian slaughterhouses

Bovine cysticercosis (BCC), caused by the helminth Taenia saginata, is currently diagnosed solely by official meat inspection (MI) based on macroscopic detection of viable cysticerci or typical lesions of degenerated larvae. MI has a known low sensitivity (<16%), leading to a large proportion of infected cattle carcasses entering the human food chain and posing a risk to public health. Prevalence in Belgium based on MI results is estimated at around 0.22%. Due to the low sensitivity of MI, alternative techniques to detect BCC should be considered. This study evaluates MI, MI with additional incisions in the heart, specific antibody detection against excretory/secretory (E/S) in the Ab-ELISA and circulating antigens in the B158/B60 Ag-ELISA on 715 (101 MI-positive and 614 MI-negative) samples collected from carcasses at slaughterhouses in Belgium. Full dissection of the predilection sites was considered the reference test. During the study, mostly carcasses with (very) light infections were detected containing predominantly degenerated or calcified cysticerci and only few viable cysticerci. Dissection of the predilection sites detected 144 (23%) additional infections in the 614 MI-negative carcasses. When sequentially performing first the dissection of the predilection sites, followed by the Ag-ELISA and the Ab-ELISA, an additional 36% of MI-negative carcasses were found positive for BCC, resulting in a prevalence very much higher than the above mentioned 0.22%. The B158/B60 Ag-ELISA showed a sensitivity of 40% for the detection of carcasses containing viable cysticerci and a specificity of 100%, and detected 70 positive carcasses of which only 14 had been identified as positive during MI. If Ag-ELISA were implemented as a detection technique for BCC in the slaughterhouses, many infected carcasses would still not be detected due to the sensitivity of 40%. But as sensitivity increases with increasing number of cysticerci in the carcass, the infected carcasses passing inspection will be the ones containing only a few viable cysticerci and thus posing a smaller food safety problem. Ag-ELISA is preferred over the ES Ab-ELISA in this study, which had a sensitivity of 13.3% and a specificity of 91.7% in a population with overall low infection burdens.

Seroprevalence of Rift Valley fever in cattle along the Akagera-Nyabarongo rivers, Rwanda

Rift Valley fever (RVF) virus is caused by a zoonotic arbovirus that is endemic to eastern and southern Africa. It has also been reported in West and North Africa, Madagascar and the Arabian Peninsula. The virus is transmitted by mosquitoes, but people can also become infected while handling blood or other body fluids of animals and humans with RVF. In 2007, there was a large outbreak of RVF in Kenya, Tanzania, Sudan and Somalia. Outbreaks were also reported in South Africa in 2008-2011. The epidemiology of RVF and factors for disease occurrence in Rwanda are neither clear nor documented. Therefore, we conducted a crosssectional study from December 2012 to March 2013 to generate baseline information on RVF in cattle. Purposive sampling of cattle (n = 595) was done in six districts, and serum samples were screened with competitive enzyme-linked immunosorbent assay (ELISA). We performed a statistical analysis on the generated data, and risk factors associated with RVF seroprevalence were determined by a simple logistic regression. Overall, RVF seroprevalence was 16.8% (95% confidence interval [CI] [13.8% - 20.0%]). The highest seroprevalence was recorded in Kirehe district (36.9%) followed by Ngoma (22.3%), and the least was recorded in Nyagatare (7.9%). RVF was more likely to occur in adult cattle (19.9% [odds ratio {OR} = 1.88, 95% CI {0.98-3.61}]) compared to young cattle (10.5% [OR = 0.47, 95% CI {0.26-0.83}]). Pure exotic or cross-breeds were significantly exposed to RVF virus (seroprevalence 22.9% [OR = 4.26, 95% CI {1.82-9.99}]) in comparison to 14.1% (OR = 0.55, 95% CI [0.35-0.86]) in local breeds. Sex differences were not statistically significant. These findings indicated that cattle have been exposed to RVF virus in six districts in Rwanda with a significant risk in adult, exotic or cross-breeds in Kirehe district.

Brucella abortus is Prevalent in Both Humans and Animals in Bangladesh

To determine the role of different Brucella (B.) spp. in Bangladesh, 62 animal samples and 500 human sera were tested. Animal samples from cattle, goats and sheep (including milk, bull semen, vaginal swabs and placentas) were cultured for Brucella spp. Three test-positive human sera and all animal samples were screened by Brucella genus-specific real-time PCR (RT-PCR), and positive samples were then tested by IS711 RT-PCR to detect B. abortus and B. melitensis DNA. Only B. abortus DNA was amplified from 13 human and six animal samples. This is the first report describing B. abortus as the aetiological agent of brucellosis in occupationally exposed humans in Bangladesh. Of note is failure to detect B. melitensis DNA, the species most often associated with human brucellosis worldwide. Further studies are required to explore the occurrence of Brucella melitensis in Bangladesh.

Latent class evaluation of three serological tests for the diagnosis of human brucellosis in Bangladesh

Background

A Bayesian latent class evaluation was used to estimate the true prevalence of brucellosis in livestock farmers and patients with prolonged pyrexia (PP) and to validate three conditionally dependent serological tests: indirect ELISA (iELISA), Rose Bengal Test (RBT), and standard tube agglutination (STAT). A total of 335 sera from livestock farmers and 300 sera from PP patients were investigated.

Results

The true prevalence of brucellosis in livestock farmers and PP patients was estimated to be 1.1 % (95 % credibility interval (CrI) 0.1–2.8) and 1.7 % (95 % CrI 0.2–4.1), respectively. Specificities of all tests investigated were higher than 97.8 % (95 % CrI 96.1–99.9). The sensitivities varied from 68.1 % (95 % CrI 54.5–80.7) to 80.6 % (95 % CrI 63.6–93.8). The negative predictive value of all the three tests in both populations was very high and more than 99.5 % (95 % CrI 98.6–99.9). The positive predictive value (PPV) of all three tests varied from 27.9 % (95 % CrI 3.6–62.0) to 36.3 % (95 % CrI 5.6–70.5) in livestock farmers and 39.8 % (95 % CrI 6.0–75.2) to 42.7 % (95 % CrI 6.4–83.2) in patients with PP. The highest PPV were 36.3 % for iELISA and 42.7 % for RBT in livestock farmers and pyrexic patients, respectively.

Conclusions

In such a low prevalence scenario, serology alone does not help in diagnosis and thereby therapeutic decision-making. Applying a second test with high specificity and/or testing patients having history of exposure with known risk factors and/or testing patients having some clinical signs and symptoms of brucellosis may increase the positive predictive value of the serologic tests.

Electronic supplementary material

The online version of this article (doi:10.1186/s41182-016-0031-8) contains supplementary material, which is available to authorized users.

Seroprevalence of brucellosis in patients with prolonged fever in Bangladesh

Introduction: This study describes the seroprevalence of human brucellosis among pyretic patients and detection of Brucella abortus DNA from seropositive pyretic patients using real-time polymerase chain reaction (rtPCR) for the first time in Bangladesh. Methodology: Blood samples were collected from 300 pyretic patients from October 2007 to May 2008 and subjected to three serological tests: Rose-Bengal plate test (RBT), standard tube agglutination test (STAT), and indirect enzyme-linked immunosorbent assay (iELISA). Risk factors were identified by multivariate Firth’s logistic regression analysis. Brucella genus (BCSP31) and species-specific (IS711) rtPCR were applied to six human sera samples. Results: The seroprevalence of brucellosis among pyretic patients was estimated to be 2.0% (95% confidence interval [CI]: 0.74–4.30). The odds of brucellosis seropositivity were 8.9 (95% CI: 1.26–63.0) times higher in pyretic patients who handled goats than those who handled only cattle, whereas the odds of brucellosis seropositivity were 9.7 (95% CI: 1.28–73.68) times higher in pyretic patients who had backache compared to those without backache. B. abortus DNA was amplified from all six human sera that tested positive by RBT, STAT, and iELISA. As the agreement between the tests was very strong, RBT is recommended as a screening test for the diagnosis of human brucellosis in Bangladesh because it is easier to use, cheaper, and faster. Conclusions: Brucellosis among pyretic patients is common, and B. abortus is responsible for brucellosis in such patients. Pyretic patients who handle goats and those with backaches should be screened for brucellosis.

Bovine and Caprine Brucellosis in Bangladesh: Bayesian evaluation of four serological tests, true prevalence, and associated risk factors in household animals

A cross-sectional study was carried out to estimate the true prevalence of Brucella spp. and identify allied risk factors/indicators associated with brucellosis in the Dinajpur and Mymensingh districts of Bangladesh. A total 320 stratified random blood samples were collected and tested in parallel for Brucella antibodies using Rose Bengal (RBT), slow agglutination (SAT), and indirect and competitive ELISA. In addition, a structured questionnaire was administered to each household herd owner to gather information regarding potential risk factors. Both univariate and multivariate logistic regression analyses were used to identify potential risk factors or indicators at animal level. A Bayesian approach was used to estimate the true prevalence of brucellosis along with the test performances (Se and Sp). The estimated animal level true prevalence in cattle was 9.70 % (95 % CPI 5.0-16 %) and in goat 6.3 % (95 % CPI 2.8-11.0 %). The highest sensitivity was achieved by SAT ranges from 69.6 to 78.9 %, and iELISA was found to be more specific (97.4 to 98.8 %) in comparison with other tests. On the other hand, a significant level of (P < 0.05) Brucella seropositivity was found in cattle that breed naturally compared with those that undergo artificial insemination. In goats, exotic breeds were significantly associated (P < 0.05) with Brucella seroprevalence compared with indigenous breeds. Goats with a previous records of abortion and/or retained placenta were also found to have significant levels (P < 0.05). Cows with previous abortion records showed higher odds (18 times) of being seropositive. None of the evaluated tests can be recommended to apply alone for the diagnosis of bovine and caprine brucellosis.

Identification of risk factors for Campylobacter contamination levels on broiler carcasses during the slaughter process

Campylobacter carcass contamination was quantified across the slaughter line during processing of Campylobacter positive batches. These quantitative data were combined together with information describing slaughterhouse and batch related characteristics in order to identify risk factors for Campylobacter contamination levels on broiler carcasses. The results revealed that Campylobacter counts are influenced by the contamination of incoming birds (both the initial external carcass contamination and the colonization level of caeca) and the duration of transport and holding time that can be linked with feed withdrawal period. In addition, technical aspects of the slaughter process such as a dump based unloading system, electrical stunning, lower scalding temperature, incorrect setting of plucking, vent cutter and evisceration machines were identified as risk factors associated with increased Campylobacter counts on processed carcasses. As such the study indicates possible improvements of the slaughter process that can result in better control of Campylobacter numbers under routine processing of Campylobacter positive batches without use of chemical or physical decontamination. Moreover, all investigated factors were existing variations of the routine processing practises and therefore proposed interventions are practically and economically achievable.

A Mycobacterial Perspective on Tuberculosis in West Africa: Significant Geographical Variation of M. africanum and Other M. tuberculosis Complex Lineages

BACKGROUND

Phylogenetically distinct Mycobacterium tuberculosis lineages differ in their phenotypes and pathogenicity. Consequently, understanding mycobacterial population structures phylogeographically is essential for design, interpretation and generalizability of clinical trials. Comprehensive efforts are lacking to date to establish the West African mycobacterial population structure on a sub-continental scale, which has diagnostic implications and can inform the design of clinical TB trials.

METHODOLOGY/PRINCIPAL FINDINGS

We collated novel and published genotyping (spoligotyping) data and classified spoligotypes into mycobacterial lineages/families using TBLineage and Spotclust, followed by phylogeographic analyses using statistics (logistic regression) and lineage axis plot analysis in GenGIS, in which a phylogenetic tree constructed in MIRU-VNTRplus was analysed. Combining spoligotyping data from 16 previously published studies with novel data from The Gambia, we obtained a total of 3580 isolates from 12 countries and identified 6 lineages comprising 32 families. By using stringent analytical tools we demonstrate for the first time a significant phylogeographic separation between western and eastern West Africa not only of the two M. africanum (West Africa 1 and 2) but also of several major M. tuberculosis sensu stricto families, such as LAM10 and Haarlem 3. Moreover, in a longitudinal logistic regression analysis for grouped data we showed that M. africanum West Africa 2 remains a persistent health concern.

CONCLUSIONS/SIGNIFICANCE

Because of the geographical divide of the mycobacterial populations in West Africa, individual research findings from one country cannot be generalized across the whole region. The unequal geographical family distribution should be considered in placement and design of future clinical trials in West Africa.

Community-based tsetse fly control significantly reduces fly density and trypanosomosis prevalence in Metekel Zone, Northwest, Ethiopia

African animal trypanosomosis is a great obstacle to livestock production where tsetse flies play a major role. Metekel zone is among the tsetse-infested areas. Community-based tsetse fly and trypanosomosis control using targets was conducted from June 2011 to May 2012 in Metekel zone, Ethiopia, to decrease trypanosomosis and tsetse fly. Cloth screen targets were developed, impregnated with 0.1 % deltamethrin, and deployed alongside rivers by the research team together with the community animal health workers. Monthly parasitological and entomological data were collected, processed, and compared with similar data collected before control. Overall average tsetse fly (Glossina tachinoides) density decreased from 1.13 to 0.18 fly/trap/day after control. The density was decreased in all sites with no significant difference among the sites. However, higher decrements were observed in the dry and late dry seasons by more than 12 and 6 times, respectively. The reduction in overall apparent prevalence of trypanosomosis caused by Trypanosoma congolense, Trypanosoma brucei, and Trypanosoma vivax from 12.14 % before to 3.61 % after control coincides with the tsetse fly reduction. In all the study sites, significant reduction was observed before and after control. The highest decrement was observed in the late dry season when the apparent prevalence was reduced from 7.89 to 1.17 % before and after control, respectively. As this approach is simple, cost-effective, and appropriate for riverine tsetse species, we recommend to be scaled up to other similar places.

Distribution and Potential Indicators of Hospitalized Cases of Neurocysticercosis and Epilepsy in Ecuador from 1996 to 2008

Background

Epilepsy is one of the most common signs of Neurocysticercosis (NCC). In this study, spatial and temporal variations in the incidence of hospitalized cases (IHC) of epilepsy and NCC in Ecuadorian municipalities were analyzed. Additionally, potential socio-economic and landscape indicators were evaluated in order to understand in part the macro-epidemiology of the Taenia solium taeniasis/cysticercosis complex.

Methodology

Data on the number of hospitalized epilepsy and NCC cases by municipality of residence were obtained from morbidity-hospital systems in Ecuador. SatScan software was used to determine whether variations in the IHC of epilepsy and NCC in space and time. In addition, several socio-economic and landscape variables at municipality level were used to study factors intervening in the macro-epidemiology of these diseases. Negative Binomial regression models through stepwise selection and Bayesian Model Averaging (BMA) were used to explain the variations in the IHC of epilepsy and NCC.

Principal findings

Different clusters were identified through space and time. Traditional endemic zones for NCC and epilepsy, recognized in other studies were confirmed in our study. However, for both disorders more recent clusters were identified. Among municipalities, an increasing tendency for IHC of epilepsy, and a decreasing tendency for the IHC of NCC were observed over time. In contrast, within municipalities a positive linear relationship between both disorders was found. An increase in the implementation of systems for eliminating excrements would help to reduce the IHC of epilepsy by 1.00% (IC_95%; 0.2%–1.8%) and by 5.12% (IC_95%; 3.63%-6.59%) for the IHC of NCC. The presence of pig production was related to IHC of NCC.

Conclusion/Significance

Both disorders were related to the lack of an efficient system for eliminating excrements. Given the appearance of recent epilepsy clusters, these locations should be studied in depth to discriminate epilepsies due to NCC from epilepsies due to other causes. Field studies are needed to evaluate the true prevalence of cysticercosis in humans and pigs in different zones of the country in order to better implement and manage prevention and/or control campaigns.

T. solium neurocysticercosis is considered the most important parasitic disease of the central nervous system in humans; it is estimated to be responsible for at least one third of acquired epilepsies in developing countries. In Ecuador, the relationship between acquired epilepsy and neurocysticercosis remains unclear due to different factors such as, the lack of specialized health care personnel, appropriate diagnostic techniques and the fact that acquired epilepsy is characteristic of many other infectious and non-infectious diseases in the endemic zones of the country. In this study, spatio-temporal information and potential socio-economic indicators were studied for the number of hospitalized neurocysticercosis and epileptic cases in the country in order to locate and characterize important clusters in space and time. This study identified traditional endemic clusters in the highlands for both conditions as well as new clusters appearing in recent years in other zones not considered endemic. Also the incidence of hospitalized cases of epilepsy and neurocysticercosis were significantly higher in urban zones, probably due to a better access to health facilities. The presence of systems for excrement disposal was significantly associated with a reduction in the incident cases for both epilepsy and neurocysticercosis. More studies are needed to evaluate the true prevalence of neurocysticercosis associated epilepsy in humans and cysticercosis in pigs around the country in order to better implement and manage control campaigns.

Association between microbiological and serological prevalence of human pathogenic Yersinia spp. in pigs and pig batches

Pigs are the main reservoir of human pathogenic Y. enterocolitica, and the microbiological and serological prevalence of this pathogen differs between pig farms. The infection status of pig batches at moment of slaughter is unknown while it is a possibility to classify batches. A relation between the presence of human pathogenic Yersinia spp. and the presence of antibodies could help to predict the infection of the pigs prior to slaughter. Pigs from 100 different batches were sampled. Tonsils and pieces of diaphragm were collected from 7047 pigs (on average 70 pigs per batch). The tonsils were analyzed using a direct plating method and the meat juice collected from the pieces of diaphragm was analyzed by Enzyme Linked ImmunoSorbent Assay. The microbiological and serological results were compared using a mixed-effects logistic regression at pig and batch level. Yersinia spp. were found in 2031 (28.8%) pigs, antibodies were present in 4692 (66.6%) pigs. According to the logistic regression, there was no relation at pig level between the presence of Yersinia spp. in tonsils and the presence of antibodies. Contrarily, at batch level, a mean activity value of 37 Optical Density (OD)% indicated a Yersinia spp. positive farm and the microbiological prevalence in pig batches could be estimated before shipment to the slaughterhouse. This offers the opportunity to classify batches based on their potential risk to contaminate carcasses with human pathogenic Yersinia spp.

Modelling the potential of focal screening and treatment as elimination strategy for Plasmodium falciparum malaria in the Peruvian Amazon Region

Background

Focal screening and treatment (FSAT) of malaria infections has recently been introduced in Peru to overcome the inherent limitations of passive case detection (PCD) and further decrease the malaria burden. Here, we used a relatively straightforward mathematical model to assess the potential of FSAT as elimination strategy for Plasmodium falciparum malaria in the Peruvian Amazon Region.

Methods

A baseline model was developed to simulate a scenario with seasonal malaria transmission and the effect of PCD and treatment of symptomatic infections on the P. falciparum malaria transmission in a low endemic area of the Peruvian Amazon. The model was then adjusted to simulate intervention scenarios for predicting the long term additional impact of FSAT on P. falciparum malaria prevalence and incidence. Model parameterization was done using data from a cohort study in a rural Amazonian community as well as published transmission parameters from previous studies in similar areas. The effect of FSAT timing and frequency, using either microscopy or a supposed field PCR, was assessed on both predicted incidence and prevalence rates.

Results

The intervention model indicated that the addition of FSAT to PCD significantly reduced the predicted P. falciparum incidence and prevalence. The strongest reduction was observed when three consecutive FSAT were implemented at the beginning of the low transmission season, and if malaria diagnosis was done with PCR. Repeated interventions for consecutive years (10 years with microscopy or 5 years with PCR), would allow reaching near to zero incidence and prevalence rates.

Conclusions

The addition of FSAT interventions to PCD may enable to reach P. falciparum elimination levels in low endemic areas of the Amazon Region, yet the progression rates to those levels may vary substantially according to the operational criteria used for the intervention.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-0868-4) contains supplementary material, which is available to authorized users.

Assessment of Risk Factors for a High Within-Batch Prevalence of Yersinia enterocolitica in Pigs Based on Microbiological Analysis at Slaughter

The purpose of the current study was to find farm-level factors influencing the bacteriological prevalence of Yersinia enterocolitica in pigs at time of slaughter. On 100 farms, data concerning a broad range of farm aspects (e.g., management and housing system, biosecurity, and hygiene measurements) were collected using a face-to-face questionnaire. At the slaughterhouse, tonsils of on average 70 slaughter pigs per batch were sampled to determine the infection status of pigs. After univariable mixed-effect logistic regressions, variables that were related to the Yersinia prevalence (p<0.05) were included in a multivariable model. In this model, the factors remaining positively associated with a higher Y. enterocolitica carriage in the tonsils (p<0.1) were an increasing number of piglet suppliers, a high density of pig farms in the area, and the use of semislatted floors in the fattening pig unit. The proper use of a disinfection bath before entering the stables and a poor biosecurity level were protective factors, although a higher prevalence was associated with a significant positive interaction between the presence of pets in the stables and a poor biosecurity level. Reducing the number of piglet suppliers, using a disinfection bath properly, and prohibiting pets inside the stables could be easily implemented by pig farmers to lower the prevalence of Y. enterocolitica in pigs at slaughter.

Epidemiology of Trypanosoma evansi and Trypanosoma vivax in domestic animals from selected districts of Tigray and Afar regions, Northern Ethiopia

Background

African animal trypanosomosis, transmitted cyclically by tsetse flies or mechanically by other biting flies, causes serious inflictions to livestock health. This study investigates the extent of non-tsetse transmitted animal trypanosomosis (NTTAT) by Trypanosoma (T.) evansi and T. vivax in domestic animals in the tsetse-free regions of Northern Ethiopia, Afar and Tigray.

Methods

A cross sectional study was conducted on 754 dromedary camels, 493 cattle, 264 goats, 181 sheep, 84 donkeys, 25 horses and 10 mules. The microhaematocrit centrifugation technique was used as parasitological test. Plasma was collected for serodiagnosis with CATT/T.evansi and RoTat 1.2 immune trypanolysis (ITL) while buffy coat specimens were collected for molecular diagnosis with T. evansi type A specific RoTat 1.2 PCR, T. evansi type B specific EVAB PCR and T. vivax specific TvPRAC PCR.

Results

The parasitological prevalence was 4.7% in Tigray and 2.7% in Afar and significantly higher (z = 2.53, p = 0.011) in cattle (7.3%) than in the other hosts. Seroprevalence in CATT/T.evansi was 24.6% in Tigray and 13.9% in Afar and was significantly higher (z = 9.39, p < 0.001) in cattle (37.3%) than in the other hosts. On the other hand, seroprevalence assessed by ITL was only 1.9% suggesting cross reaction of CATT/T.evansi with T. vivax or other trypanosome infections. Molecular prevalence of T. evansi type A was 8.0% in Tigray and in Afar and varied from 28.0% in horses to 2.2% in sheep. It was also significantly higher (p < 0.001) in camel (11.7%) than in cattle (6.1%), donkey (6%), goat (3.8%), and sheep (2.2%). Four camels were positive for T. evansi type B. Molecular prevalence of T. vivax was 3.0% and was similar in Tigray and Afar. It didn’t differ significantly among the host species except that it was not detected in horses and mules.

Conclusions

NTTAT caused by T. vivax and T. evansi, is an important threat to animal health in Tigray and Afar. For the first time, we confirm the presence of T. evansi type B in Ethiopian camels. Unexplained results obtained with the current diagnostic tests in bovines warrant particular efforts to isolate and characterise trypanosome strains that circulate in Northern Ethiopia.

Estimation of canine Leishmania infection prevalence in six cities of the Algerian littoral zone using a Bayesian approach

A large-scale study on canine Leishmania infection (CanL) was conducted in six localities along a west-east transect in the Algerian littoral zone (Tlemcen, Mostaganem, Tipaza, Boumerdes, Bejaia, Jijel) and covering two sampling periods. In total 2,184 dogs were tested with an indirect fluorescent antibody test (IFAT) and a direct agglutination test (DAT). Combined multiple-testing and several statistical methods were compared to estimate the CanL true prevalence and tests characteristics (sensitivity and specificity). The Bayesian full model showed the best fit and yielded prevalence estimates between 11% (Mostaganem, first period) and 38% (Bejaia, second period). Sensitivity of IFAT varied (in function of locality) between 86% and 88% while its specificity varied between 65% and 87%. DAT was less sensitive than IFAT but showed a higher specificity (between 80% and 95% in function of locality or/and season). A general increasing trend of the CanL prevalence was noted from west to east. A concordance between the present results and the incidence of human cases of visceral leishmaniasis was observed, where also a maximum was recorded for Bejaia. The results of the present study highlight the dangers when using IFAT as a gold standard.

Mathematical inference on helminth egg counts in stool and its applications in mass drug administration programmes to control soil-transmitted helminthiasis in public health

In the present study, we present a hierarchical model based on faecal egg counts (FECs; expressed in eggs per 1g of stool) in which we first describe the variation in FECs between individuals in a particular population, followed by describing the variance due to counting eggs under a microscope separately for each stool sample. From this general framework, we discuss how to calculate a sample size for assessing a population mean FEC and the impact of an intervention, measured as reduction in FECs, for any scenario of soil-transmitted helminth (STH) epidemiology (the intensity and aggregation of FECs within a population) and diagnostic strategy (amount of stool examined (∼sensitivity of the diagnostic technique) and examination of individual/pooled stool samples) and on how to estimate prevalence of STH in the absence of a gold standard. To give these applications the most wide relevance as possible, we illustrate each of them with hypothetical examples.

Inter-epidemic acquisition of Rift Valley fever virus in humans in Tanzania

Background

In East Africa, epidemics of Rift Valley fever (RVF) occur in cycles of 5–15 years following unusually high rainfall. RVF transmission during inter-epidemic periods (IEP) generally passes undetected in absence of surveillance in mammalian hosts and vectors. We studied IEP transmission of RVF and evaluated the demographic, behavioural, occupational and spatial determinants of past RVF infection.

Methodology

Between March and August 2012 we collected blood samples, and administered a risk factor questionnaire among 606 inhabitants of 6 villages in the seasonally inundated Kilombero Valley, Tanzania. ELISA tests were used to detect RVFV IgM and IgG antibodies in serum samples. Risk factors were examined by mixed effects logistic regression.

Findings

RVF virus IgM antibodies, indicating recent RVFV acquisition, were detected in 16 participants, representing 2.6% overall and in 22.5% of inhibition ELISA positives (n = 71). Four of 16 (25.0%) IgM positives and 11/71 (15.5%) of individuals with inhibition ELISA sero-positivity reported they had had no previous contact with host animals. Sero-positivity on inhibition ELISA was 11.7% (95% CI 9.2–14.5) and risk was elevated with age (odds ratio (OR) 1.03 per year; 95% CI 1.01–1.04), among milkers (OR 2.19; 95% CI 1.23–3.91), and individuals eating raw meat (OR 4.17; 95% CI 1.18–14.66). Households keeping livestock had a higher probability of having members with evidence of past infection (OR = 3.04, 95% CI = 1.42–6.48) than those that do not keep livestock.

Conclusion

There is inter-epidemic acquisition of RVFV in Kilombero Valley inhabitants. In the wake of declining malaria incidence, these findings underscore the need for clinicians to consider RVF in the differential diagnosis for febrile illnesses. Several types of direct contact with livestock are important risk factors for past infection with RVFV in this study’s population. However, at least part of RVFV transmission appears to have occurred through bites of infected mosquitoes.

Rift Valley fever (RVF) is a disease of animals and people that is caused by the RVF virus. During epidemics, humans get RVF through direct contact with animals or through mosquito bites. In East Africa, epidemics occur every 5–15 years following unusually high rainfall. In between epidemics, the transmission of RVF might occur at low level. In an epidemic-free period, we measured whether people in the Kilombero Valley in Tanzania had evidence of past and recent RVF infection in their blood sample, and studied risk factors. Three per cent of people had been infected recently, and 12% had evidence of past infection, with increased risk with age, among milkers and among people eating raw meat. Some people with past or recent infection reported they had not had contact with animals. Households keeping livestock had more members with evidence of past infection. The findings show that people get infected with RVF in between epidemics, and that various types of contact with livestock are important risk factors. There is also evidence that some people get infected with RVFV by mosquitoes in the epidemic free period. Clinicians in the Kilombero Valley should consider RVF in the differential diagnosis of patients with fever.

Measuring general animal health status: Development of an animal health barometer

The development of an animal health barometer, an instrument to measure the general health of the Belgian livestock population on a yearly basis and to monitor its evolution over time, is described. The elaboration of a set of 13 animal health indicators (AHIs) as the basis for the animal health barometer is discussed. These indicators were weighted by experts - including scientists, policy makers and agro-industrial representatives - to determine their relative weight in the barometer. The result of the barometer is expressed as a comparison with a previous year. Based on the results of the 13 AHIs, it is concluded that general animal health in Belgium shows a positive evolution since 2008. The animal health barometer provides a composite view of the status of livestock health in Belgium and is a tool to communicate in an intelligible, comprehensible manner on aspects of animal health to consumers and professional stakeholders in the animal production and food chain. Together with the food safety barometer (Baert et al., 2011. Food Res. Int. 44, 940) and the plant health barometer (Wilmart et al., 2014. Eur. J. Plant Pathol. doi: 10.1007/s10658-014-0547-x), the animal health barometer is one of the three instruments to provide a holistic view on the overall status of the safety of the food chain in Belgium.

Improved molecular detection of Ehrlichia and Anaplasma species applied to Amblyomma ticks collected from cattle and sheep in Ethiopia

Detection of Ehrlichia and Anaplasma species in animals and tick vectors is crucial for an understanding of the epidemiology of diseases caused by these pathogens. In this study, a pair of primers designated EBR2 and EBR3 was designed from the Anaplasma 16S rDNA sequence and was used along with a previously described primer EHR 16SD for the simultaneous detection of Ehrlichia and Anaplasma species by nested PCR. The primers were used to amplify 925bp of DNA from known species of Ehrlichia and Anaplasma. Restriction with MboII and MspI enzymes allowed Ehrlichia and Anaplasma speciation. Restriction with MboII differentiated between An. marginale, Anaplasma (formerly Ehrlichia) sp. Omatjenne, and An. centrale with An. marginale and Anaplasma (formerly Ehrlichia) sp. Omatjenne yielding 2 distinct fragments each while An. centrale produced 3 distinct bands. Ehrlichia ruminantium and An. phagocytophylum remained undigested. Subsequent restriction with MspI differentiated E. ruminantium from An. phagocytophylum with 2 and 4 fragments, respectively. When used on tick samples from the field, 63 ticks (16.4%) out of 384 collected from cattle and sheep were positive for one or more species of Ehrlichia and Anaplasma. The positivity ranged from 6.3% at Andasa to 36.7% at Habernosa. Higher overall infection rates were found in Amblyomma lepidum than in Amblyomma variegatum ticks (p=0.009). Amblyomma lepidum from Habernosa were more often infected with all detected species of Anaplasma and Ehrlichia than Am. variegatum. At Bako, however, Anaplasma (formerly Ehrlichia) sp. Omatjenne was detected only in Am. variegatum. A significantly higher proportion of ticks collected from cattle (20.6%) was found positive than in those collected from sheep (3.3%) (p=0.003). Simultaneous detection of Ehrlichia and Anaplasma species and correct identification of mixed infections was possible. Since the ticks were collected from animals, the occurrence of the major species of Ehrlichia and Anaplasma in ruminants in the area is confirmed.

Epidemiology of visceral leishmaniasis in Algeria: an update

Visceral leishmaniasis (VL), a zoonotic disease caused by Leishmania infantum, is endemic in Algeria. This report describes a retrospective epidemiological study conducted on human VL to document the epidemiological profile at national level. All human VL cases notified by the National Institute of Public Health between 1998 and 2008 were investigated. In parallel all VL cases admitted to the university hospitals of Algiers were surveyed to estimate the underreporting ratio. Fifteen hundred and sixty-two human VL cases were reported in Algeria between 1998–2008 with an average annual reported incidence rate of 0.45 cases per 100,000 inhabitants, of which 81.42% were in the age range of 0–4 years. Cases were detected year-round, with a peak notification in May and June. One hundred and seventy patients were admitted to the university hospitals in Algiers in the same period, of which less than one in ten had been officially notified. Splenomegaly, fever, pallor and pancytopenia were the main clinical and laboratory features. Meglumine antimoniate was the first-line therapy for paediatric VL whereas the conventional amphotericin B was used for adult patients. Visceral leishmaniasis in Algeria shows the epidemiological profile of a paediatric disease with a decrease of the annual reported incidence rate. However, vigilance is required because of huge underreporting and an apparent propagation towards the south.

Estimation of hepatitis E virus (HEV) pig seroprevalence using ELISA and Western blot and comparison between human and pig HEV sequences in Belgium

Zoonotic transmission of hepatitis E virus (HEV) is of special concern, particularly in high income countries were waterborne infections are less frequent than in developing countries. High HEV seroprevalences can be found in European pig populations. The aims of this study were to obtain prevalence data on HEV infection in swine in Belgium and to phylogenetically compare Belgian human HEV sequences with those obtained from swine. An ELISA screening prevalence of 73% (95% CI 68.8-77.5) was determined in Belgian pigs and a part of the results were re-evaluated by Western blot (WB). A receiver operating characteristic curve analysis was performed and scenarios varying the ELISA specificity relative to WB were analysed. The seroprevalences estimated by the different scenarios ranged between 69 and 81% and are in agreement with the high exposure of the European pig population to HEV. Pig HEV sequences were genetically compared to those detected in humans in Belgium and a predominance of genotype 3 subtype f was shown in both swine and humans. The high HEV seroprevalence in swine and the close phylogenetic relationships between pig and human HEV sequences further support the risk for zoonotic transmission of HEV between humans and pigs.

Human brucellosis in northwest Ecuador: typifying Brucella spp., seroprevalence, and associated risk factors

Human brucellosis in Ecuador is underreported and based only on passive surveillance. Since 2008, brucellosis was removed from the list of communicable diseases in the country. Until now, the true human brucellosis picture has not yet been determined. The aim of this study was to determine the seroprevalence of the disease, identify risk factors associated with brucellosis seropositivity in humans, and isolate circulating strains of Brucella spp. in the northwestern part of Ecuador. Between 2006 and 2008, a large transect survey was conducted, based on blood sampling of people from the northwestern part of Ecuador (n=3733) together with an epidemiological inquiry. On the basis of three diagnostic tests used in parallel, the overall seroprevalence was estimated as 1.88% (95% confidence interval [CI] 1.48-2.38). Based on a multivariable random effects logistic regression analysis, the main risk factors associated with human brucellosis seropositivity were contact with livestock (odds ratio [OR]=3.0; CI 1.25-7.08), consumption of fetus and placenta (OR=2.5; CI 1.18-5.22), and involvement in activities at risk for brucellosis infection (OR=1.8; CI 1.00-3.35). Noticeable variation in brucellosis seropositivity among humans within cantons was observed. The circulating strain was Brucella abortus biotype 4. This study emphasized that contact with livestock, consumption of fetus and placenta, and occupational hazard group were all significant risk factors for the transmission of brucellosis among individuals in the northwestern part of Ecuador. Alongside encouraging the launching of educational campaigns against brucellosis, especially in rural areas where 36% of the population lives, controlling this zoonotic disease in animals will directly benefit its prevention in humans, especially because there is no safe and efficacious vaccine against brucellosis in humans.

Lack of evidence for safe vaccination with the Muguga cocktail in Sudan

How to cite this article: Geysen, D. & Berkvens, D., 2013, ‘Lack of evidence for safe vaccination with the Muguga cocktail in Sudan’, Onderstepoort Journal of Veterinary Research 80(1), Art. #571, 1 page. http:// dx.doi.org/10.4102/ojvr. v80i1.571

Inter-epidemic transmission of Rift Valley fever in livestock in the Kilombero River Valley, Tanzania: a cross-sectional survey

BACKGROUND

In recent years, evidence of Rift Valley fever (RVF) transmission during inter-epidemic periods in parts of Africa has increasingly been reported. The inter-epidemic transmissions generally pass undetected where there is no surveillance in the livestock or human populations. We studied the presence of and the determinants for inter-epidemic RVF transmission in an area experiencing annual flooding in southern Tanzania.

METHODOLOGY

A cross-sectional sero-survey was conducted in randomly selected cattle, sheep and goats in the Kilombero river valley from May to August 2011, approximately four years after the 2006/07 RVF outbreak in Tanzania. The exposure status to RVF virus (RVFV) was determined using two commercial ELISA kits, detecting IgM and IgG antibodies in serum. Information about determinants was obtained through structured interviews with herd owners.

FINDINGS

An overall seroprevalence of 11.3% (n = 1680) was recorded; 5.5% in animals born after the 2006/07 RVF outbreak and 22.7% in animals present during the outbreak. There was a linear increase in prevalence in the post-epidemic annual cohorts. Nine inhibition-ELISA positive samples were also positive for RVFV IgM antibodies indicating a recent infection. The spatial distribution of seroprevalence exhibited a few hotspots. The sex difference in seroprevalence in animals born after the previous epidemic was not significant (6.1% vs. 4.6% for females and males respectively, p = 0.158) whereas it was significant in animals present during the outbreak (26.0% vs. 7.8% for females and males respectively, p<0.001). Animals living >15 km from the flood plain were more likely to have antibodies than those living <5 km (OR 1.92; 95% CI 1.04-3.56). Species, breed, herd composition, grazing practices and altitude were not associated with seropositivity.

CONCLUSION

These findings indicate post-epidemic transmission of RVFV in the study area. The linear increase in seroprevalence in the post-epidemic annual cohorts implies a constant exposure and presence of active foci transmission preceding the survey.

Spatio-temporal clusters of incident human brucellosis cases in Ecuador

This study aimed to determine whether variations in the incidence of reported cases of human brucellosis in Ecuador were clustered in space and time. In addition, the effects of cattle and small ruminant population density and other socio-economic factors on the incidence were investigated. Significant space-time clusters were found in the northern and southern highlands and parts of Ecuadorian Amazonia. Customs of people, cattle, goat and sheep population density appeared to influence the incidence of brucellosis. In this study, the incidence of reported cases of human brucellosis was found to be higher in the highlands (sierra) and in municipalities near Peru and Colombia. The results of this study highlight the need for prevention and control measures aimed at abating the incidence of brucellosis among livestock and humans.

Bayesian estimation of true prevalence, sensitivity and specificity of indirect ELISA, Rose Bengal Test and Slow Agglutination Test for the diagnosis of brucellosis in sheep and goats in Bangladesh

The true prevalence of brucellosis and diagnostic test characteristics of three conditionally dependent serological tests were estimated using the Bayesian approach in goats and sheep populations of Bangladesh. Serum samples from a random selection of 636 goats and 1044 sheep were tested in parallel by indirect ELISA (iELISA), Rose Bengal Test (RBT) and Slow Agglutination Test (SAT). The true prevalence of brucellosis in goats and sheep were estimated as 1% (95% credibility interval (CrI): 0.7-1.8) and 1.2% (95% CrI: 0.6-2.2) respectively. The sensitivity of iELISA was 92.9% in goats and 92.0% in sheep with corresponding specificities of 96.5% and 99.5% respectively. The sensitivity and specificity estimates of RBT were 80.2% and 99.6% in goats and 82.8% and 98.3% in sheep. The sensitivity and specificity of SAT were 57.1% and 99.3% in goats and 72.0% and 98.6% in sheep. In this study, three conditionally dependent serological tests for the diagnosis of small ruminant brucellosis in Bangladesh were validated. Considerable conditional dependence between IELISA and RBT and between RBT and SAT was observed among sheep. The influence of the priors on the model fit and estimated parameter values was checked using sensitivity analysis. In multiple test validation, conditional dependence should not be ignored when the tests are in fact conditionally dependent.

[Detection of processed animal protein: European experience and perspectives]

European Commission Regulation (EC) No. 152/2009 imposes optical microscopy as the reference method for official controls to detect traces of animal protein in animal feed. Since 1 July 2004, the one-solvent technique has been the only authorised variant of optical microscopy. Its detection limit is 0.1% of meat-and-bone meal. Other techniques--using molecular biology (polymerase chain reaction, immunology), microscopy or near-infrared imaging--have been developed in the past ten years to supplement the official method, which has certain limitations. This paper compares and discusses the different techniques, highlighting the strengths of each technique in order to propose a feasible control scheme to improve the sensitivity and specificity of the technique for the detection of processed animal protein in livestock feed.