Seroepidemiological survey of trypanozoon infection in horses in the suspected dourine-infected Bale highlands of the Oromia region, Ethiopia

This paper presents the results of a seroepidemiological survey of trypanozoon infection in horses carried out between September 2007 and June 2008. The survey was conducted to determine the seroprevalence of anti-trypanozoon antibodies in 880 serum samples collected randomly from selected horse-breeding districts of the Bale highlands of Ethiopia. The seroprevalence of trypanozoon infection was found to be 173 (19.66%) and 140 (15.91%) for the CATT/T. evansi and LATEX/T. evansi tests, respectively. The high seroprevalence of trypanozoon infection strongly indicates that the infection is endemic. Neither test can differentiate between anti-trypanozoon antibodies caused by infection with T. equiperdum (the causative agent of dourine) and those of T. evansi (the causative agent of surra). The findings of the present study suggest that field-applicable screening serological tests such as the CATT/T. evansi and LATEX/T. evansi could be useful for epidemiological studies and the control of trypanozoon infection.     

Tenth international meeting on Trypanosoma evansi: report of the working group. Paris, 24 May 1989

Some epidemiological surveys have provided information on the incidence of Trypanosoma evansi infection among dromedaries in Mali, and among buffaloes in Java and Indonesia. The disease among camels has been reported again from Kazakhstan in the USSR, with the coexistence of T. evansi and Cephalopina titillator in animals which developed acute infection. The disease has been studied among horses in Venezuela and among buffaloes in Vietnam and Indonesia, and suspected among horses in Brazil. Diagnostic kits for rapid and reliable detection of T. evansi are being made available free of charge, upon request, by the institutes which have developed these new techniques, namely: detecting the parasite by agglutination-lysis; detecting antibody (by a modification of CATT); detecting antigen (by using monoclonal antibodies). Once these various diagnostic procedures developed by competent institutes have been evaluated and used widely, the next step will be to standardise the techniques and the antigens. Differential diagnosis of T. evansi and T. equiperdum is still difficult in the case of akinetoplastic strains. For improved evaluation of T. evansi isolates, a proposal has been made to form collections of complementary DNA (cDNA) with a view to exchanging these copies and the original strains. The advice of the International Commission on Zoological Nomenclature has been requested for definitive adoption of a binomial designation for the species T. evansi. With more extensive data on the pharmacology and pharmacokinetics of Cymelarsan and laboratory testing of a new trypanocide called "IMOL 881", research on trypanocides continues.     

Eleventh international meeting on Trypanosoma evansi: report of the Working Group. Paris, 17 May 1990.

Three objectives have been achieved by the Working Group since its creation in 1983: more detailed information (and consequently better awareness) of zones infected by T. evansi; refinement of diagnostic techniques and the development of test kits suitable for field use; development of a new synthetic trypanocide. Exchange of strains between specialist laboratories should be encouraged in order to compare isolates from Africa, Asia and South America by using current techniques of biotechnology, and to open the way to better knowledge of the pathogenicity of T. evansi and to the discovery of effective prophylactic measures. Research reported to the meeting was concerned with the taxonomy and genetics of T. evansi, the cloning and sequencing of nuclear and kinetoplastic DNA (kDNA), chromosomal polymorphism in relation to antigenic variation, the detection of lymphocytic interleukin 2 and its receptors in infected ponies, the use of monoclonal group antibodies to detect T. evansi, and the importance of natural receptivity of the host. A text concerning the diagnosis of surra (T. evansi infection) was drafted and forwarded to the Office International des Epizooties (OIE) for incorporation in the OIE Manual of recommended diagnostic techniques and requirements for biological products. A concise dossier was presented on the pharmacology and pharmacodynamics of the new trypanocide, melarsomine (proprietary name Cymelarsan). The recommended active dosage was 0.25 mg/kg body weight, given as a single intramuscular or subcutaneous injection. Laboratory tests were also reported with ronidazole, demonstrating its trypanocidal activity in rats.     

Characterisation of a monoclonal antibody against Trypanosoma evansi and its application for detecting circulating antibodies

Monoclonal antibodies were obtained against Trypanosoma evansi. The 2-4F6 IgM monoclonal antibody (Mab) was chosen for the study because of its ability to detect antigens and its specificity (as it did not recognise T. cruzi, T. equiperdum, Babesia equi or B. caballi). The immunoblot test revealed that the 2-4F6 IgM Mab recognises epitopes in two antigenic bands, one measuring 85 kDa and the other 122 kDa. An immunoassay for antigen detection in serum using polyclonal antibodies for capture, the Mab 2-4F6 as primary antibody and an antimouse IgM as secondary antibody gave positive results in 10 of the 11 equidae infected with T. evansi, whereas 20 controls gave negative results. These research results show that the Mab 2-4F6 and the antigen it recognises are useful in identifying equidae infected with T. evansi.     

The contribution of quality assurance to national veterinary organizations in developing countries: the case of Africa

Food safety has, within a few years, become an essential concern for producers and consumers, especially in Western countries, but also in Africa. African countries are increasingly aware of the issues involved, and of the need to react and to implement appropriate strategies in order to avoid public health risks and obstacles to their export markets. Most countries recognise that the overall sanitary quality of foodstuffs produced and distributed in the region must be improved. The OIE (World organisation for animal health) recommends that Veterinary Services attempt to improve the safety of animal products by establishing a framework of risk management, throughout the food chain, which will reduce risks by eliminating or controlling hazards during the first stages of processing. The activities of Veterinary Services, from the organisational, technical, financial and human resource points of view, must be guided by quality assurance considerations, pursuant to the standards laid down in the Terrestrial Animal Health Code of the OIE. The quality of Veterinary Services depends therefore on a range of factors, including fundamental ethical, organisational and technical principles. It goes without saying that ethical principles cannot be effective unless the Veterinary Services have the resources necessary to reinforce them. The implementation of quality assurance by the Veterinary Services in developing countries, and particularly in Africa, will promote better organisation, effective use of limited resources, and professionalism in decision-making. It will also allow for better access to international markets thanks to certification recognised by the OIE and the international community.     

Harmonisation of European tests for serological diagnosis of Brucella infection in bovines

The principal methods for the serological diagnosis of bovine brucellosis are the complement fixation test (CFT), serum agglutination test (SAT), Rose-Bengal test (RBT), indirect enzyme-linked immunosorbent assay (iELISA) and more recently the competitive ELISA (cELISA) and the fluorescent polarisation assay (FPA). Guidelines set by the World Organisation for Animal Health (OIE) describe methods and diagnostic thresholds for each of these tests. Many countries have adopted these methods for the purposes of eradication of brucellosis and have legislated for the use of these tests (the CFT and SAT in particular) for the prevention of the spread of the disease through international trade. Within the European Union (EU) each member state has a National Reference Laboratory which regulates the quality of brucellosis diagnosis and works to the recommendations set by the OIE. This article describes the results from the first three EU ring trials assessing the harmonisation of diagnostic tests between each member state. The general level of harmony for SAT, CFT, and iELISA was found to be good, but issues of standardisation of the RBT, cELISA and FPA remain. The cELISA and FPA in particular need further work to create European harmony. The ring trials also proved successful at providing specific evidence of poor performance in some areas. The decision on whether or not to take action on the basis of these results rested with the individual laboratories concerned. The increase in the number of participants in these trials over time reflected the enlargement of the EU and increased the need for quality assurance.     

Report of the Twelfth International Meeting of the OIE Ad hoc Group on Non Tsetse-Transmitted Animal Trypanosomosis. Paris, 15 May 1991.

Studies of Trypanosoma evansi strains of widely varied origin (Africa, Asia, South America) have continued, leading to two groups of diagnostic procedures, tested first in the laboratory and then in the field: the card agglutination trypanosomosis test and the enzyme-linked immunosorbent assay to supplement microscopic examination of smears. A microscopy procedure for differentiating Trypanosoma species in smears was proposed. Diagnostic kits have again been made available free of charge to interested and suitably qualified research workers. Several research workers have studied the lymphokines induced by T. evansi, and the question of the potential therapeutic use of these substances was raised. Research workers in Asia were increasingly involved in various problems associated with T. evansi, including fundamental research and potential applications in the field. The epidemiology of T. evansi infections has been the subject of numerous research projects in Asia and South America. Research on trypanocides has confirmed the activity of Cymelarsan, which has since been marketed, the properties of the new derivative T46 (pharmacokinetic studies) and the value of in vitro and in vivo comparisons of currently available trypanocides. The sphere of interest of the Group was extended to cover all forms of animal trypanosomosis not transmitted by tsetse flies.     

Genetic characterization of Trypanosoma evansi isolated from a patient in India.

The first human case of trypanosomiasis caused by Trypanosoma evansi was recently discovered in India. We have focused on the parasite to investigate whether this atypical infection was due to a particular genotype of T. evansi. The SRA gene was not detected by PCR in the Indian human T. evansi (TEVH) DNA sample. TEVH appears to be closely related to Vietnam WH, with identical alleles for TRBPA and MT30-33 AC/TC microsatellites. Furthermore, T. evansi has homogeneous kDNA minicircles and the minicircles of isolate TEVH were shown to be of Type A. Thus, the T. evansi isolated from an Indian patient appears to be a typical T. evansi as far as we can judge, suggesting that the explanation for this unusual infection may lie with the patient.     

The influence of economic indicators, poultry density and the performance of veterinary services on the control of high-pathogenicity avian influenza in poultry

High-pathogenicity avian influenza (HPAI) and low-pathogenicity notifiable avian influenza (LPNAI) in poultry are notifiable diseases that must be reported to the World Organisation for Animal Health (OIE). There are variations between countries' responses to avian influenza (AI) outbreak situations based on their economic status, diagnostic capacity and other factors. The objective of this study was to ascertain the significant association between HPAI control data and a country's poultry density, the performance of its Veterinary Services, and its economic indicators (gross domestic product, agricultural gross domestic product, gross national income, human development index and Organisation for Economic Co-operation and Development [OECD] status). Results indicate that as poultry density increases for least developed countries there is an increase in the number and duration of HPAI outbreaks and in the time it takes to eradicate the disease. There was no significant correlation between HPAI control and any of the economic indicators except membership of the OECD. Member Countries, i.e. those with high-income economies, transparency and good governance, had shorter and significantly fewer HPAI outbreaks, quicker eradication times, lower mortality rates and higher culling rates than non-OECD countries. Furthermore, countries that had effective and efficient Veterinary Services (as measured by the ratings they achieved when they were assessed using the OIE Tool for the Evaluation of Performance of Veterinary Services) had better HPAI control measures.     

Mechanisms for collaboration between public and private veterinarians: the animal health accreditation mandate

There are several examples of national collaboration between official Veterinary Services and the private sector, in both developed and developing countries. In developed countries national veterinary systems tend to have a 'centripetal' structure: from the private to the somewhat centralised public system, whilst in developing countries there is currently the reverse, i.e. a 'centrifugal' movement. Faced with international quality requirements for national Veterinary Services, the institutional foundations for the execution of certain official activities by the private sector are provided by the OIE (World organisation for animal health), particularly in the Terrestrial Animal Health Code. The private sector should however be employed using clear formal procedures governed by various legally recognised systems. At this level, the animal health accreditation mandate has the advantage of combining within a single concept several legal benefits associated with each type of collaboration. Moreover, it can encourage private veterinarians to work in the field, and to continue to do so for a reasonable length of time, thus providing a de facto territorial network of competent, logistically independent professionals, acting as ad hoc public service agents for both the design and implementation of animal health related activities, all at an economic cost that does not compromise the budget of the national Veterinary Services. By making savings in terms of human and material resources, the animal health accreditation mandate appears to be particularly suitable for developing countries where means of communication and intervention often come up against unforeseen logistical difficulties.     

The importance of governance and reliable veterinary certification

Good veterinary certification is possible only if a country's veterinary governance complies with the quality standards of the World Organisation for Animal Health (OIE). The standards in the OIE Terrestrial Animal Health Code stipulate that the main prerequisite for good veterinary governance is for Veterinary Services to be independent, that is to say they are able to carry out their mandate while remaining autonomous and free from any commercial, financial, hierarchical or political pressures that could lead them to make technical decisions that were contrary to OIE standards. Veterinary Services should include, in particular, a veterinary administration with nationwide jurisdiction for implementing the animal health measures and veterinary certification procedures recommended by the OIE and for overseeing or auditing their implementation. They should also include veterinary authorities and persons authorised by the veterinary statutory body to perform tasks under the responsibility and supervision of a veterinarian (veterinary paraprofessionals). This veterinary governance must be sustainable over time in order to administer long-term animal health policies. Good governance relies on appropriate legislation that is in compliance with OIE guidelines and on the requisite human and financial resources for ensuring its enforcement. The evaluation of this governance, either by an importing country in the context of international trade, as authorised by OIE standards, or by the country itself (self-evaluation or an evaluation requested from the OIE [using the OIE Tool for the Evaluation of Performance of Veterinary Services]), helps to facilitate the proper operation of Veterinary Services and to ensure the reliability of any certification granted under the authority of the veterinary administration.     

Epidemiology and diagnosis of African trypanosomiasis using DNA probes

The accurate identification of trypanosome species has been a challenging problem in the epidemiology of African trypanosomiasis, both human and animal. The last 10 years have seen great progress through the application of deoxyribonucleic acid (DNA) probe technology, although this has also revealed greater complexity than supposed. While a single repetitive DNA probe can identify all members of the subgenus Trypanosoma (Trypanozoon), including the human pathogens T. brucei gambiense and T. b. rhodesiense as well as the non-tsetse-transmitted trypanosomes T. evansi and T. equiperdum, at least 6 probes are needed to distinguish members of the subgenus Nannomonas, in which only 2 species, T. congolense and T. simiae, were previously recognized. Similarly, the subgenus Duttonella appears to consist of more than one species. Use of this battery of DNA probes to identify the trypanosomes carried by tsetse flies in the field has yielded some surprises about the accuracy (or inaccuracy) of previous identification methods. An unexpectedly high prevalence of mixed infections has been found in all the field studies carried out so far. The large number of infections that remain unidentified by the available probes suggests the existence of other, as yet unknown, trypanosome species. Limited use of the polymerase chain reaction has been made for diagnosis of human and animal trypanosomiasis, due to its high cost.     

Characterization of Trypanosoma evansi type B.

A distinctive feature of Trypanosoma evansi is the possession of a kinetoplast that contains homogeneous DNA minicircles, but lacks DNA maxicircles. Two major sequence variants of the minicircle have been described and here we have sequenced the type B variant and designed a specific PCR test to distinguish it from type A. Further a test based on maxicircles to distinguish T. brucei brucei from T. evansi was designed and evaluated. Using the designed PCR tests, we detected three type B isolates from camel blood samples collected in northern Kenya, more than 20 years after the first isolation of type B. Comparison of minicircle sequences from all four type B isolates shows >96% identity within the group, and 50-60% identity to type A minicircles. Phylogenetic analysis based on minicircle sequences reveals two clusters, one comprising isolates of type A and one of type B, while random amplification of polymorphic DNA show slight polymorphic bands within type B. Most T. evansi isolates analysed were heterozygous at a repetitive coding locus (MORF2). All type B isolates had one genotype designated 3/5 based on the alleles present. Three camel isolates, which had homogenous type A minicircles, lacked the RoTat 1.2 gene, while another five isolates were T. b. brucei, based on the heterogeneity of their minicircles and presence of maxicircles as demonstrated by PCR amplification of the gene for cytochrome oxidase subunit 1. Our results confirm the existence of T. evansi type B isolates, T. b. brucei and existence of T. evansi type A without RoTat 1.2 gene in Kenyan isolates.     

Further evidence from SSCP and ITS DNA sequencing support Trypanosoma evansi and Trypanosoma equiperdum as subspecies or even strains of Trypanosoma brucei

The subgenus Trypanozoon includes three species Trypanosoma brucei, Trypanosoma evansi and Trypanosoma equiperdum, which are morphologically identical and indistinguishable even using some molecular methods. In this study, PCR-based single strand conformation polymorphism (PCR-SSCP) was used to analyze the ribosomal DNA of the Trypanozoon species. Data indicate different patterns of ITS2 fragments between T. brucei, T. evansi and T. equiperdum by SSCP. Furthermore, analysis of total ITS sequences within these three members of the subgenus Trypanozoon showed a high degree of homology using phylogenetic analysis but were polyphyletic in haplotype networks. These data provide novel nuclear evidence to further support the notion that T. evansi and T. equiperdum should be subspecies or even strains of T. brucei.     

The organisation and functioning of Veterinary Services: results of a 2005 survey of Member Countries of the World Organisation for Animal Health

A questionnaire was sent to the 167 Member Countries of the World Organisation for Animal Health (OIE) in 2004 and 2005. The organisation and functioning of national Veterinary Services were analysed based on the responses from 85 of these countries. Leaving aside variations between countries, Veterinary Services are very involved in animal health and food safety controls at farm level (including animal feed), and during primary and secondary processing, whether alone or in conjunction with other services. At the lower end of the chain, namely distribution and the food service industry, responsibilities tend to be more widely shared. Veterinary Services have a central responsibility in international trade in animals and animal products. The main weaknesses in the chain of controls concern the logistical and financial resources of Veterinary Services, and insufficient involvement of livestock producers and even of field veterinarians. The many recent reforms are tending to provide a more consistent, integrated approach to animal health and food safety controls 'from the stable to the table'.     

The organisation of federal Veterinary Services in Canada: the Canadian Food Inspection Agency

The organisational design of a national Veterinary Service is critical to the overall quality and integrity of its animal health and veterinary public health infrastructure. It is well recognised that the diversity of political, economic and social situations which exist in and between countries dictates that no one model of organisational structure can be applied to all circumstances. In Canada, a re-organisation of the approach of the federal government to food inspection in 1997 resulted in the transfer of the veterinary administration to a newly created agency called the Canadian Food Inspection Agency (CFIA). The authors provide a short background on the impetus for the creation of the CFIA and an overview of its organisational structure and responsibilities in animal and veterinary public health and food safety. Also included are the logic models that were developed for the federal Veterinary Services as part of their quality and performance management framework. Integrating all federally mandated food inspection systems under the CFIA has had concrete benefits in clarifying roles and responsibilities, reducing overlap and duplication of programme functions, improving service delivery and facilitating federal-provincial collaboration. Moreover, the strength of the organisation lies in the ability of the Canadian Veterinary Services to adhere to the fundamental principles of quality which are recommended by the OIE (World organisation for animal health) for the evaluation of Veterinary Services. No single organisational structure can guarantee a highly effective or competent Veterinary Service. Common challenges exist that may or may not be addressed in whole or in part by the organisational structure. The challenges highlighted in this paper provide further thoughts on the management of shared jurisdiction, meeting public health objectives, balancing science and political accountability, and defining the role and jurisdiction of veterinarians.     

Treatment and follow-up of the first case of human trypanosomiasis caused by Trypanosoma evansi in India

The first reported human case of trypanosomiasis caused by Trypanosoma evansi was treated using suramin. Patient follow-up indicates that the drug and specific regimen used were well tolerated. Clinical, serological and parasitological investigations at 6 months indicate complete cure of the patient. Suramin should be considered in the treatment of other cases of human T. evansi infection, if they occur.     

Genetic diversity of Trypanosoma evansi in beef cattle based on internal transcribed spacer region.

This study was focused on genetic diversity of Trypanosoma evansi which is a widely distributed haemoflagellate of veterinary importance that infects a variety of larger mammals including horses, mules, camels, buffalo, cattle and deer. The genetic diversity of T. evansi of beef cattle LAM19 was accomplished by using phylogenetic analysis based on internal transcribed spacer region (ITS). Blood sample was collected from a naturally infected beef cattle LAM 19 and parasitemia was raised by mouse inoculation. The parasites were collected and isolated by using DE 52 DEAE cellulose anion exchange column prior to DNA extraction. Upon PCR amplification of ITS region, the product of 1300bp in size was obtained. The ITS nucleotide sequences were analyzed and revealed that it could demonstrate the genetic diversity of T. evansi of beef cattle LAM19. Based on the ITS tree, beef cattle LAM 19 T. evansi were categorized into two main groups where the genetic diversity occurred within Group 1. The data could be applicable for the survey of parasite dynamics, epidemiological studies as well as prevention and control of the disease.     

Antimicrobial resistance and the standards of the World Organisation for Animal Health

Antimicrobial resistance and the use of antimicrobial agents in veterinary medicine are complex issues that are currently a source of major international concern. It is therefore essential for the World Organisation for Animal Health (OIE) to consider this issue, while at the same time continuing to address the problem of zoonotic diseases. That is why the OIE has included objectives for veterinary drugs, especially antimicrobials, in its Strategic Plan. The OIE plays an active part in discussions on this subject in conjunction with other international organisations working in this field, such as the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO). Furthermore, the OIE has adopted guidelines both for defining harmonised methodologies for antimicrobial resistance surveillance and monitoring and for helping countries to conduct a risk analysis tailored to their situation and to take appropriate management measures. The OIE has included this issue in its programme of assistance to countries by offering them structural enhancement tools: the Tool for the Evaluation of Performance of Veterinary Services (O1E PVS Tool), PVS Gap Analysis, veterinary legislation support, and training for veterinary national focal points, with the aid of its Collaborating Centres for veterinary medicinal products. Only by mobilising all countries to improve the quality of antimicrobials, to introduce antimicrobial resistance surveillance and to implement measures for the responsible and prudent use of antimicrobials, will it be possible to halt the spread of antimicrobial resistance.     

The obligations of Member Countries of the OIE (World Organisation for Animal Health) in the Organisation of Veterinary Services

The authors discuss the mission, organisation and resources of Veterinary Services in the new international trading environment and examine how the standards for Veterinary Services, contained in the OIE (World Organisation for Animal Health) International Animal Health Code (the Code), help provide the necessary support for Veterinary Services to meet their rights and obligations under the provisions of the Sanitary and Phytosanitary (SPS) Agreement of the World Trade Organization (WTO). The authors describe the challenges of gaining access to international trading markets through surveillance and control of OIE listed diseases. Finally, the approach in the Code to the principles underpinning the quality of Veterinary Services and to guidelines for evaluating Veterinary Services, is discussed.