Pig-farming systems and porcine cysticercosis in the north of Cameroon

A survey was conducted in 150 households owning 1756 pigs in the rural areas of Mayo-Danay division in the north of Cameroon. A questionnaire survey was carried out to collect information on the pig-farming system and to identify potential risk factors for Taenia solium cysticercosis infection in pigs. Blood samples were collected from 398 pigs with the aim of estimating the seroprevalence of T. solium cysticercosis. The results showed that 90.7% of the pigs are free roaming during the dry season and that 42.7% of households keeping pigs in the rural areas have no latrine facility. Seventy-six per cent of the interviewed pig owners confirmed that members of the household used open-field defecation. Enzyme-linked immunosorbent assay (ELISA) for antigen and antibody detection showed an apparent prevalence of cysticercosis of 24.6% and 32.2%, respectively. A Bayesian approach, using the conditional dependence between the two diagnostic tests, indicated that the true seroprevalence of cysticercosis in Mayo-Danay was 26.6%. Binary logistic regression analysis indicated that a lack of knowledge of the taeniasis–cysticercosis complex and the absence of a pig pen in the household were associated with pig cysticercosis

Prevalence of Taenia solium cysticercosis in pigs entering the food chain in western Kenya

Three hundred forty-three pigs slaughtered and marketed in western Kenya were subjected to lingual examination and HP10 Ag-ELISA for the serological detection of Taenia solium antigen. When estimates were adjusted for the sensitivity and specificity of the diagnostic assays, prevalence of T. solium cysticercosis estimated by lingual exam and HP10 Ag-ELISA was between 34.4 % (95 % confidence interval (CI) 19.4–49.4 %) and 37.6 % (95 % CI 29.3–45.9 %), respectively. All pigs, however, were reported to have passed routine meat inspection. Since T. solium poses a serious threat to public health, these results, if confirmed, indicate that the introduction of control strategies may be appropriate to ensure the safety of pork production in this region

A Research Agenda for Helminth Diseases of Humans: Intervention for Control and Elimination

Recognising the burden helminth infections impose on human populations, and particularly the poor, major intervention programmes have been launched to control onchocerciasis, lymphatic filariasis, soil-transmitted helminthiases, schistosomiasis, and cysticercosis. The Disease Reference Group on Helminth Infections (DRG4), established in 2009 by the Special Programme for Research and Training in Tropical Diseases (TDR), was given the mandate to review helminthiases research and identify research priorities and gaps. A summary of current helminth control initiatives is presented and available tools are described. Most of these programmes are highly dependent on mass drug administration (MDA) of anthelmintic drugs (donated or available at low cost) and require annual or biannual treatment of large numbers of at-risk populations, over prolonged periods of time. The continuation of prolonged MDA with a limited number of anthelmintics greatly increases the probability that drug resistance will develop, which would raise serious problems for continuation of control and the achievement of elimination. Most initiatives have focussed on a single type of helminth infection, but recognition of co-endemicity and polyparasitism is leading to more integration of control. An understanding of the implications of control integration for implementation, treatment coverage, combination of pharmaceuticals, and monitoring is needed. To achieve the goals of morbidity reduction or elimination of infection, novel tools need to be developed, including more efficacious drugs, vaccines, and/or antivectorial agents, new diagnostics for infection and assessment of drug efficacy, and markers for possible anthelmintic resistance. In addition, there is a need for the development of new formulations of some existing anthelmintics (e.g., paediatric formulations). To achieve ultimate elimination of helminth parasites, treatments for the above mentioned helminthiases, and for taeniasis and food-borne trematodiases, will need to be integrated with monitoring, education, sanitation, access to health services, and where appropriate, vector control or reduction of the parasite reservoir in alternative hosts. Based on an analysis of current knowledge gaps and identification of priorities, a research and development agenda for intervention tools considered necessary for control and elimination of human helminthiases is presented, and the challenges to be confronted are discussed

Characterization of S3Pvac Anti-Cysticercosis Vaccine Components: Implications for the Development of an Anti-Cestodiasis Vaccine

Background: Cysticercosis and hydatidosis seriously affect human health and are responsible for considerable economic loss in animal husbandry in non-developed and developed countries. S3Pvac and EG95 are the only field trial-tested vaccine candidates against cysticercosis and hydatidosis, respectively. S3Pvac is composed of three peptides (KETc1, GK1 and KETc12), originally identified in a Taenia crassiceps cDNA library. S3Pvac synthetically and recombinantly expressed is effective against experimentally and naturally acquired cysticercosis.Methodology/ Principal Findings: In this study, the homologous sequences of two of the S3Pvac peptides, GK1 and KETc1, were identified and further characterized in Taenia crassiceps WFU, Taenia solium, Taenia saginata, Echinococcus granulosus and Echinococcus multilocularis. Comparisons of the nucleotide and amino acid sequences coding for KETc1 and GK1 revealed significant homologies in these species. The predicted secondary structure of GK1 is almost identical between the species, while some differences were observed in the C terminal region of KETc1 according to 3D modeling. A KETc1 variant with a deletion of three C-terminal amino acids protected to the same extent against experimental murine cysticercosis as the entire peptide. on the contrary, immunization with the truncated GK1 failed to induce protection. Immunolocalization studies revealed the non stage-specificity of the two S3Pvac epitopes and their persistence in the larval tegument of all species and in Taenia adult tapeworms.Conclusions/ Significance: These results indicate that GK1 and KETc1 may be considered candidates to be included in the formulation of a multivalent and multistage vaccine against these cestodiases because of their enhancing effects on other available vaccine candidates

Animal influence on water, sanitation and hygiene measures for zoonosis control at the household level: A systematic literature review

Neglected zoonotic diseases (NZDs) have a significant impact on the livelihoods of the world’s poorest populations, which often lack access to basic services. Water, sanitation and hygiene (WASH) programmes are included among the key strategies for achieving the World Health Organization’s 2020 Roadmap for Implementation for control of Neglected Tropical Diseases (NTDs). There exists a lack of knowledge regarding the effect of animals on the effectiveness of WASH measures. This review looked to identify how animal presence in the household influences the effectiveness of water, hygiene and sanitation measures for zoonotic disease control in low and middle income countries; to identify gaps of knowledge regarding this topic based on the amount and type of studies looking at this particular interaction

TSOL18 vaccine antigen of Taenia solium: development of monoclonal antibodies and field testing of the vaccine in Cameroon

Chapter 1 reviews the literature about the immunological aspects of taeniid cestode infections and the existing vaccines against Taenia solium cysticercosis in pigs. One of the most promising vaccines is TSOL18, a protein that has been identified in the oncosphere of Taenia solium and expressed as a recombinant molecule in E. coli. Repeated experimental trials have shown that this vaccine is able to protect up to 100% of the immunised pigs against a challenge infection with T. solium. Antibodies raised by the vaccine are capable of killing the parasite in in vitro cultures and it is believed that antibody and complement mediated killing of invading parasites is the major protective immune mechanism induced by vaccination with TSOL18. The identification of the villages with a high risk of T. solium infection, which could subsequently be used in the vaccine trial, is reported in chapter 2. A survey was conducted in 150 households owning 1756 pigs in the rural areas of Mayo-Danay division in the far north region of Cameroon. A questionnaire survey was carried out to collect information on the pig farming system and to identify potential risk factors for T. solium cysticercosis infection in pigs. Blood samples were collected from 398 pigs with the aim of estimating the sero-prevalence of Taenia solium cysticercosis. The results showed that 90.7% of the pigs were free roaming during the dry season and that 42.7% of households keeping pigs in the rural areas had no latrine facility. Seventy six percent of the interviewed pig owners affirmed that the members of the household used open field defecation. ELISA for antigen and antibody detection showed an apparent prevalence of porcine cysticercosis of 24.6% and 32.2%, respectively. A Bayesian approach using the conditional dependence between the two diagnostic tests indicated that the true sero-prevalence of cysticercosis in Mayo-Danay was 26.6%. Binary logistic regression analysis indicated that the lack of knowledge of the taeniasis-cysticercosis complex and the absence of a pig pen in the household were associated with pig cysticercosis. Chapter 3 reports the investigations that were undertaken to characterise whether the principal antibody specificities raised by TSOL18 in pigs were against linear or conformational determinants. TSOL18 was expressed in two truncated forms representing either the amino terminal portion or the carboxy terminal portion, with the two truncations overlapping in sequence by 25 amino acids. The original protein (designated TSOL18N—) and the two truncations (TSOL18N—-1 and TSOL18N—-2) were used in inhibition ELISA to determine their ability to inhibit the binding of protective pig antibodies to TSOL18. TSOL18N— was shown to be capable of completely inhibiting the binding of pig anti-TSOL18N— antibodies to TSOL18N— in ELISA. However, neither TSOL18N—-1 nor TSOL18N—-2, either alone or combined, was capable of inhibiting any detectable amount of reactivity of pig anti-TSOL18N— antibodies with TSOL18N—. It is concluded that the dominant antibody specificities, and likely the host-protective specificities, of TSOL18 are conformational epitopes. Chapter 4 describes the development of an antibody detection test for the specific diagnosis of porcine cysticercosis. A fraction with a major band of 14 kDa was obtained from crude cyst fluid (CF) of T. solium cysticerci by 2-step chromatography. A first fraction isolated by gel filtration was purified using an anion exchange column on High Performance Liquid Chromatography (HPLC). Evaluation of the analytic sensitivity of this fraction (F3) was carried out in an antibody detection enzyme-linked immunosorbent assay (Ab-ELISA-F3) using serum samples from pigs experimentally infected with different doses of T. solium eggs. The cross-reactivity of F3 was evaluated with serum samples from pigs that were naturally or experimentally infected with Taenia hydatigena, Taenia saginata asiatica, Fasciola hepatica, Trichinella spiralis, Metastrongylus apri, Trypanosoma congolense or Sarcoptes scabiei, and with serum samples of rabbits hyper-immunised with cyst fluid of T. hydatigena or T. solium. Analysis of the specificity of the F3 showed that serum samples of pigs infected with other parasites did not recognise this antigen. Cross-reaction with T. hydatigena occurred in ELISA using CF as antigen, but the F3 antigen fraction was not recognized by the rabbit hyper-immune serum against T. hydatigena. Evaluation of the diagnostic sensitivity and specificity of the Ab-ELISA-F3 was done by a non-parametric Receiver Operating Characteristic (ROC) analysis using serum samples from Zambian and Cameroonian village pigs. The results from the ROC analysis yielded a low diagnostic value (area under ROC curve= 0.48) with the sera from the Zambian pigs while a relatively high diagnostic value was obtained with the sera from Cameroonian pigs (area under ROC curve= 0.78). In Chapter 5 the efficacy of the TSOL18 vaccine is assessed under field conditions in the Mayo-Danay district. Two hundred and forty 2-3 month old piglets belonging to 114 individual households were involved in the study. In each household one or more pairs of piglets were included, with one animal of each pair being vaccinated and the other acting as a non-vaccinated control. Vaccinated animals received two initial immunizations intramuscularly in the neck one month apart with 200μg TSOL18 plus 5mg Quil A. At the time of the second immunization both vaccinated and control animals received an oral dose of 30mg/kg oxfendazole. Vaccinated animals received a third immunization approximately 3 months after the first immunization. Antibody responses to the vaccine were assessed at different time intervals by ELISA. Necropsies were undertaken when the pigs were approximately 12 months of age. All parasites were counted in half of the body musculature and in the brain. Two hundred and twelve animals were available for necropsy at the end of the trial (110 vaccinated; 102 controls). Viable T. solium cysticerci were identified in 20 control pigs (prevalence 19.6%), including 14 animals that had estimated total body burdens of > 1000 cysticerci. No cysticerci were found in any of the vaccinated animals indicating that the vaccine provided a very high level of protection (P< 0.0001) against naturally acquired infection with T. solium in pigs. Combined application of TSOL18 vaccination and a single oxfendazole treatment in pigs is a simple and relatively sustainable procedure that has the potential to control T. solium transmission in endemic areas and, indirectly, reduce the number of new cases of neurocysticercosis in humans. In chapter 6, the similarity of the antibody responses of pigs and mice to TSOL18 antigen is highlighted. Four IgG1 monoclonal antibodies (MoAb) were produced against the conformational epitopes of TSOL18. It was shown that pig antisera inhibit the binding of these MoAbs in a competition ELISA, indicating that pig and mouse antibodies against TSOL18 vaccine react with the same conformational epitopes. For this reason, monoclonal antibodies raised in mice immunized with TSOL18 could be a valuable source of antibodies for further characterisation of the host-protective epitopes of the vaccine. A monoclonal antibody-based inhibitive enzyme-linked immunosorbent assay (mi-ELISA) was developed. Serum samples of TSOL18-vaccinated and non-vaccinated pigs were used. In all the vaccinated and protected pigs screened at necropsy, anti-TSOL18 antibodies inhibited the binding of a monoclonal antibody (Mab25D12C1) specific to the conformational epitopes of TSOL18 antigen, suggesting an immune response that correlates with protection. This result was in agreement with the results obtained in an indirect ELISA, which showed that all the vaccinated and protected pigs had developed antibodies to the TSOL18 vaccine. In chapter 7 the efficacy of the TSOL18 vaccine is compared with that of other vaccines, which are currently being tested under field conditions. Recommendations are made for implementing a vaccination programme in Cameroon. Future research activities are suggested to improve our knowledge on the duration of the immunity of the vaccine and various other aspects of the vaccine production and delivery

Taenia solium taeniosis/cysticercosis in Africa: Risk factors, epidemiology and prospects for control using vaccination

Poor sanitary conditions, free-roaming of domestic pigs and lack of awareness of the disease play an important role in the perpetuation of the Taenia solium taeniosis and cysticercosis in Africa. Traditional pig production systems known as the source of T. solium taeniosis/cysticercosis complex are predominant in the continent, representing 60-90% of pig production in rural areas. It has been reported that T. solium cysticercosis is the main cause of acquired epilepsy in human population and results in considerable public health problems and economic costs to the endemic countries. Although the socioeconomic impact and public health burden of cysticercosis have been demonstrated, up to now no large-scale control programme has been undertaken in Africa. Most disease control trials reported in the literature have been located in Latin America and Asia. This review discusses the risk factors and epidemiology of T. solium cysticercosis in Africa and critically analyzes the options available for implementing control of this zoonotic disease in the continent