Detection of Mycobacterium spp. in slaughter cattle at Gauteng abattoirs

Prevalence and characterization of Mycobacterium spp. in slaughter cattle at Gauteng abattoirs: Food safety implications for meat consumers-A pilot study

Industry Sector: Cattle And Small Stock

Research Focus Area: Animal Health & Welfare

Research Institute: ARC – Onderstepoort Veterinarary Institute

Researcher: Dr Tiny Hlokwe

Team:

Title Initials Surname Highest Qualification Research Institution
Mrs V Mareledwane MSc ARC-OVR
Title Initials Surname Highest Qualification Research Institution
Prof AA Adesiyun PhD University of Pretoria
Prof P Thompson PhD University of Pretoria

Year of completion : 2020

Aims Of The Project

  • To isolate and identify Mycobacterium spp. from granulomatous/tuberculous lesions, lymph nodes (i.e. mesenteric, supra-mammary, retropharyngeal and internal iliac) and lungs of slaughter cattle
  • To determine the prevalence of bovine tuberculosis in slaughter cattle in selected abattoirs (high throughput, low throughput and rural/informal by using cell-mediated immune assays.
  • To characterize the isolates of Mycobacterium spp. recovered from cattle regarding their species identification and genotypes.
  • To obtain demographic information on farm management (feedlot, cow-calf or communal); animal information (age: adult or young, sex: male or female; and breed) by linking abattoir data back to the farms of origin and to visit farms from which seropositive animals originated to assess the existing risk factors for infection.

Executive Summary

Tuberculosis is a disease that is caused by a group of acid-fast gram-positive bacteria belonging to the Mycobacterium tuberculosis complex. Tuberculosis has a wide species range but not all species are equally susceptible and are divided into maintenance hosts and spillover hosts. M. tuberculosis is mostly the causative agent in humans while M. bovis is the predominant causative agent of tuberculosis in animals. In animals, cattle and buffaloes are the reservoirs of the disease in South Africa. TB is a zoonotic disease with great economic impact estimated to billions of dollars annually. This is because, for many farmers, cattle are a source of income. The impact is greatly felt in productivity. The zoonotic potential of the disease is a very big concern to public health. In addition, the interference of non-tuberculous mycobacteria in the diagnosis of BTB cannot be underestimated.

Globally, abattoirs are used for passive and active surveillance of diseases of both economic and public health significance such as tuberculosis. Surveys by serological and bacterial culture assays of slaughter animals may be used to detect newly introduced disease agents and in monitoring disease control and eradication programmes. Information generated from abattoir surveillance could provide an early warning system for impending epidemics or failures of intervention programmes such as vaccination of livestock against certain diseases, thereby allowing early intervention efforts to prevent epidemic loss of animals. Losses may result from mortality in animal population, cost of quarantine, isolation and treatment and in some cases loss of international trade. The usefulness of data obtained from abattoirs during surveillance for selected diseases is however dependent on the accuracy of the data obtained, data analysis and interpretation. Data generated from abattoirs could also be used to measure the potential health risk to farm workers, veterinarians or veterinary assistants attending to such animals, abattoir workers and consumers of products from the live animals, such as milk. The risk of zoonotic diseases, such as tuberculosis to workers who are exposed to infected animals pre-, during and post-slaughter, cannot be over-emphasized. Abattoirs in any country, if properly managed, are invaluable facilities for ensuring that only safe meat reaches the consumers, as well as preventing or reducing the potential health risk posed by infected or diseased animals to workers at these facilities.

Developed countries usually run efficient abattoirs and slaughterhouses and have effectively used them in the surveillance of diseases like tuberculosis and brucellosis in the USA, leptospirosis in New Zealand, and cystic echinococcosis in Spain. Reliable data obtained from abattoirs and slaughterhouses are used pro-actively to drive, monitor, change or formulate policies. In South Africa slaughterhouses are registered by government and closely inspected and audited for hygienic slaughter practices. Use of data obtained from these abattoirs for surveillance and diseases control purposes is however limited. The same applies to most other developing countries where, in most cases, slaughter practices in the abattoirs are not closely monitored by government and livestock diseases data are not captured and adequately used for surveillance and disease control.

In South Africa, as in most developing countries, there are also a number of unregistered informal slaughterhouses and small butcheries where virtually no hygiene monitoring, meat inspection or record keeping take place, thus creating a potential health risk to consumers. Records on zoonotic disease including Tuberculosis may be available at some abattoirs or laboratories country-wide, and these need to be accessed and analysed by researchers or veterinary officials as part of disease surveillance. This useful information may also be used for policy formulation on disease control. Furthermore, although some published reports exist on the detection of tuberculosis in livestock and wildlife diseases, the prevalence of the infections is largely unknown, particularly in communal livestock

Objective Statement

The current study was conducted at selected abattoirs in the Gauteng province, South Africa and the main objective was to determine the prevalence of livestock TB in slaughter livestock in these abattoirs using a cell-mediated immune assay (IFN-γ) and culture based methods.

Results

A total of 410 fresh blood samples were collected from slaughter livestock (369 cattle and 41 sheep) from 15 abattoirs, and analysed using Bovigam® test kit.

Of the 369 cattle sampled, valid IFN‐γ results (i.e. test samples passed quality control checks) were obtained in 318 (86.2%) of the cattle. The estimated prevalence of cattle positive for bTB was 4.4% (95% CI: 2.4-7.3%) (Table 1). Of the eight variables analysed, seven (animal species, sex, breed, district, municipalities, origin of animals and abattoir throughput) were not associated with the estimated prevalence of bTB. However, prevalence varied significantly between abattoirs (p=0.005), ranging between 3.6% (95% CI: 0.09-18.3%) in abattoir I to 23.1% (95% CI: 8.9%-43.6%) in abattoir B. The estimated prevalence of avian reactors was 5.9% (95% CI: 3.6-9.2%) (Table 2), also varying significantly between abattoirs (p=0.004), ranging from 3.6% (95% Cl: 0.09-18.3%) in abattoirs E and I to 20.7% (95% CI: 7.9-39.7%) in abattoir J. The prevalence of avian reactors in cattle was not significantly different to that of bTB. The estimated prevalence of cattle tested reacting to Mycobacterium spp. (combined bTB and avian reactors) was 10% (95% CI: 7.0-14%) (Table 3). In the univariate analysis, prevalence varied by sex of animal (3.0% in females and 11.9% in males) and by breed (5.4% in Jersey, 13% in Bonsmara, 0% in other breeds), but these differences were not significant after adjusting for confounding using exact logistic regression. Of the 41 sheep sampled, valid IFN‐γ results were obtained in 22 (54%) of the animals and none were positive for bTB nor were there any avian reactors (95% CI: 0-15%) (Table 1-3). No isolation was made from all the tissue samples cultured. However, non tuberculous mycobacteria were isolated from the environmental samples collected as confirmed by 16S rRNA gene analysis (see fig 1).

Conclusion

Meat inspection is a long-standing form of disease surveillance for both food safety and animal health. For diseases that produce slowly progressive but evident lesions, such as bTB, slaughterhouse inspection is an effective surveillance tool. The detection of positive bTB reactors in our study has, however, clearly illustrated the limitations of this method of disease surveillance, as the study also established that the abattoir source of the animals sampled significantly (p=0.005) affected the prevalence of bTB. The potential zoonotic risk of transmission to abattoir workers as well as food safety hazard to consumers, can therefore not be over-emphasized. Our study highlights the potential for the use of the IFN‐γ assay in reducing this risk. Studies have demonstrated that the use IFN‐γ assay in combination with other TB tests leads to a more accurate screening of bTB in cattle. Follow-up studies, with the intervention of the relevant area State Veterinarians, should be conducted to include using the animal information from the abattoir to trace back to the herds of origin and further testing of the whole herds.

Our study highlighted the inadequacy of meat inspection alone to detect bTB in cattle slaughtered for human consumption. It is therefore imperative to apply additional methods, such as the gamma interferon assay, to accurately determine the TB infection status in slaughter cattle from abattoirs. This approach will provide a true assessment of the risk of TB posed to abattoir workers and consumers of meat from infected cattle. Although we could not detect any Mycobacterium species by culture based method, we are not surprised by by these outcome, as all slaughtered livestock were cleared of having suspect lesions.

Popular Article

Inadequacy of Meat Inspection in the Surveillance of Bovine Tuberculosis: A Zoonotic and Food Safety Risk Concern

Authors: Vuyokazi Mareledwane1,2, Abiodun A. Adesiyun1,3, Peter N. Thompson1, Tiny M. Hlokwe4#

1 Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, 0110, South Africa. 2 Vaccines and Diagnostics Programme, Agricultural Research Council-Onderstepoort Veterinary Research, Private Bag X05, Onderstepoort, 0110, South Africa. 3 School of Veterinary Medicine, Faculty of Medical Sciences, The University of the West Indies, St. Augustine, Trinidad and Tobago. 4Diagnostic Service Programme, Agricultural Research Council-Onderstepoort Veterinary Research, Private Bag X05, Onderstepoort, 0110, South Africa.

Background

Bovine tuberculosis (bTB) is a zoonotic disease with serious consequences for the livestock and wildlife industries around the world. The causative agent, normally Mycobacterium bovis (M. bovis), has a broad host range (domestic and wild animals). Meat inspection represents a long-standing form of disease surveillance that serves both food safety and animal health.

Occurrence of bovine tuberculosis in cattle

Although test and slaughter programme reduced the prevalence in commercial cattle in South Africa, disease outbreaks in different regions of the country still occur. Bovine tuberculosis is a zoonotic disease with great economic impact estimated to be billions of dollars annually. This is because, for many farmers, cattle are a source of income. The impact is greatly felt in productivity.

Bovine tuberculosis as a zoonosis

Mycobacterium bovis is known to cause tuberculosis in both animals and humans, which makes this bacterium a potentially important zoonotic species. People are most commonly infected with M. bovis by drinking or eating contaminated and unpasteurised milk and milk products. Infection can also occur through direct contact with a wound of an infected animal during slaughter.

Use of abattoirs in the surveillance of bovine tuberculosis

Globally, abattoirs are used for passive and active surveillance of diseases, such as bTB, of both economic and public health significance. Our team, consisting of researchers from the University of Pretoria and Onderstepoort Veterinary Research recently conducted a study to investigate the prevalence of bTB in slaughter livestock at 15 abattoirs in Gauteng, South Africa. A total of 410 fresh blood samples were collected from slaughter livestock (369 cattle and 41 sheep) and analysed using Bovigam® test kit.

Outcome and implications

The estimated prevalence of the disease in cattle was 4.4% (95% CI: 2.4-7.3%), and varied among abattoirs, ranging from 0 to 23%; however, there were no significant differences among genders, breeds, municipalities, districts, origin of animal (feedlot, auction or farm) or throughput of abattoirs. None of the sheep sampled was positive for the disease. Results obtained clearly illustrated the limitation of disease surveillance using a meat inspection approach alone, considering that all the 410 slaughter animals sampled had passed visual abattoir inspection and therefore classified as free of bTB.

Zoonotic risk and food safety implications for meat consumers

Our findings therefore emphasize the zoonotic risk of transmission of bTB to abattoir workers and a potential food safety hazard to consumers. Furthermore, our study highlights the potential to use of the blood assay (Bovigam® test kit) for bTB surveillance at abattoirs.

Research Funding

The research was made possible through funds kindly provided by the Red Meat Research and Development (RMRD)-SA and the Gauteng Department of Agriculture and Rural Development (GDARD).

Figure 1 shows different ways in which bovine tuberculosis can be transmitted from cattle to people

Figure 2 show PhD students Vuyokazi Mareledwane and Maruping Mangena getting ready for abattoir sampling

Figure 3 shows a student analyzing test results in the laboratory

Please contact the Primary Researcher if you need a copy of the comprehensive report of this project –
Nicholas Rivers-Moore on blackfly1@vodamailcom

Figure 1 shows different ways in which bovine tuberculosis can be transmitted from cattle to people
Figure 2 show PhD students Vuyokazi Mareledwane and Maruping Mangena getting ready for abattoir sampling
Figure 3 shows a student analyzing test results in the laboratory

Landscape genomics in South Africa

Genomic technologies for the improvement of South African beef cattle

Industry Sector: Cattle and Small Stock

Research Focus Area: Livestock production with global competitiveness: Breeding, physiology and management

Research Institute: Agriculture Research Institute – OVI

Researcher: Dr. Pranisha Omduth Soma

Title Initials Surname Highest Qualification
Prof. A.N. Maiwashe PhD
Dr F.C. Muchadeyi PhD
Prof. E. van-Marle Koster PhD
Prof. M.M. Makgahlela PhD
Dr M. MacNeil PhD
Dr S.O. Makina PhD

Year of completion : 2018

Aims Of The Project

  • To estimate linkage disequilibrium within South African beef cattle
  • To perform a genome wide scan for signatures of selection in beef cattle
  • To sequence genomic regions targeted by selection in order to identify possible polymorphisms

Executive Summary

South African indigenous and locally developed cattle breeds possess adaptive traits that are usually associated with tolerance to various diseases, extreme temperatures and humidity, and to change in feed availability. These breeds are also adapted to low-input management systems and have shown the ability to survive, produce and reproduce under harsh environments. Thus, these breeds hold potential in the changing South African production environments. However, little is known about the nature or extent of the genetic variation underlying these breeds.

The aim of this study was to conduct a genome wide scan for signatures of selection among Afrikaner, Nguni, Drakensberger, Bonsmara, Angus and Holstein cattle breeds of South Africa using data generated from the Bovine SNP50k BeadChip. The Angus and Holstein breeds were included as reference breeds since they have been extensively characterized using similar tools.

Therefore, in this project, the Bovine SNP50 BeadChip was used to characterize the genetic diversity and population structure of SA cattle breeds, determine the linkage disequilibrium and conduct a genome wide scan for signatures of selection among the Afrikaner (n=44), Nguni (n=54), Drakensberger (n=47) and Bonsmara (n=46)., using the Angus (n=31) and Holstein (n=29) cattle reference groups.

The first experiment performed included the evaluation of the Bovine SNP50 BeadChip to determine its utility for genome wide studies of South African cattle. Results of this experiment revealed that over 50 % of the SNPs were polymorphic (eg. Nguni = 35 843), indicating that the Bovine SNP50 assay would be useful for genome wide studies among South African cattle breeds.

Information about genetic diversity and population structure among cattle breeds is essential for genetic improvement, understanding of environmental adaptation as well as utilization and conservation of cattle breeds. Genetic diversity within the cattle breeds was analyzed using three measures of genetic diversity namely allelic richness, expected heterozygosity and inbreeding coefficient. The genetic diversity and population structure analyses indicated that the Afrikaner cattle had the lowest level of genetic diversity (He=0.24) while the Drakensberger cattle (He=0.30) had the highest among indigenous and locally-developed breeds. As expected, the average genetic distance was the greatest between indigenous breeds and Bos Taurus breeds but the lowest among indigenous and locally-developed breeds. Model-based clustering revealed some level of admixture among indigenous and locally-developed breeds and supported the clustering of the breeds according to their history of origin. Clear genetic divergence between South African (indigenous and locally-developed cattle breeds) and Bos Taurus cattle breeds was observed which suggested distinct genetic resources in South African cattle breeds which should be conserved in order to cope with unpredictable environments.

The extent of linkage disequilibrium (LD) is important for determining the minimum distance between markers for effective genome coverage for genome wide association studies. It can also provide insight into the evolutionary history of a population. The analyses of the extent of linkage disequilibrium (LD) showed that Afrikaner, Angus and Holstein had higher LD compared to Nguni, Drakensberger and Bonsmara cattle at all tested genomic distances. The higher LD within the Afrikaner cattle suggested that this breed has experienced considerable selection forces in contrast to what is expected of indigenous breeds and would require lower marker (50 000) density relative to what will be required for the Nguni, Drakensberger (150 000) and Bonsmara (75 000) cattle for genome wide studies. New breeding strategies may be required for the Afrikaner cattle breed to ensure future fitness of the breed. The effective population size for the Nguni, Drakensberger and Bonsmara were above the FAO recommended level.

The detection of selection signatures among cattle breeds may assist in locating regions of the genome that are, or have been, functionally important and targeted by selection. In this study, two approaches were employed. The first was based on the detection of genomic regions for which haplotypes have been driven towards complete

Fixation within breeds. The second approach identified regions of the genome exhibiting elevated population differentiation (Fst). A total of 47 genomic regions were identified as harboring potential signatures of selection using both methods. Thirty three of these regions were successfully annotated to identify candidate genes. Among these, were keratin genes (KRT222, KRT24, KRT25, KRT26 and KRT27) and one heat shock protein (HSPB9) on chromosome 19 (BTA) at 41,447,971-41,926,734 bp in the Nguni that have been previously associated with adaptation to tropical environments in Zebu cattle.

Furthermore, a number of genes associated with nervous system (WNT5B, FMOD, PRELP, ATP2B), immune response (CYM, CDC6, CDK10), production (MTPN, IGFBP4, TGFBI, AJAPI) and reproductive (ADIPOR2, OVOS2, RBBP8) performances were detected to be under selection in this study.

Target probes for enrichment were designed from exome and 5’ and 3’ untranslated regions of the cattle genome. Many SNP’s were identified in regulatory regions, leading to conformational changes in factor-binding sites. Gene ontology enrichment and clustering, resulted in the enrichment of gene ontology terms involved in fertility-related categories. Taking advantage of the availability of the fully sequenced bovine genome, the South African beef breeds were sequenced to detect genetic variants, in particular, large-scale SNP’s, which may contribute to the beef cattle genomics in South Africa.

The results presented in this study, forms the basis for effective management of South African cattle breeds and provides a useful foundation for the detection of mutations underlying genetic variation in traits of economic importance in South African cattle breeds.

This study produced one PhD thesis, 12 peer reviewed scientific articles and one popular article.

Popular Article

Genomic technology for South African Beef Cattle

Makina¹, F.C. Muchadeyi², E. van-Marle Koster³, A. Maiwashe¹ and P. Soma¹
ARC-Animal Production Institute, Private Bag X2, Irene, South Africa; ²ARC-Biotechnology Platform, Onderstepoort, ³University of Pretoria, Department of Animal and Wildlife Sciences, Private Bag X20, Hatfield, Pretoria, South Africa.

Corresponding author, E-mail: Pranisha@arc.agric.za, Tel: +27 (0)12 672 9218

South African (SA) indigenous and locally developed cattle breeds possess adaptive traits that are usually associated with tolerance to various diseases, extreme temperatures and humidity and to change in the availability to feed. These breeds are also adapted to low-input management systems and have shown the ability to survive, produce and reproduce under harsh environments. Thus, these breeds hold potential in the changing South African production environments. Despite their large numbers and not endangered status, their adaptive traits are of importance and there is a worldwide drive for the effective management of indigenous genetic resources, as they could be most valuable in selection and breeding programs in times of biological stress such as famine, drought or disease epidemics.

The recent development in molecular genetics and bioinformatics has enabled the development of genome wide SNP DNA arrays for livestock species including cattle. These chips present opportunities to study South African cattle breeds in order to unravel population structure as well as the genetic potential of these breeds.

The Bovine SNP50 BeadChip was used to genetically characterize these breeds. The study populations comprised the Afrikaner, Nguni, Drakensberger and Bonsmara cattle breeds with the Angus and Holstein cattle as reference groups. Results of this study demonstrated that the genomic information generated from the BovineSNP50 has potential for application in South African cattle populations and allow for the unravelling of their genetic potential with regard to production, reproduction, disease resistance and adaptation.

There was a clear genetic divergence between South African (indigenous and locally-developed cattle breeds) and <em>Bos taurus</em> cattle breeds which suggested distinct genetic resources in South African cattle breeds that should be properly utilized in order to cope with unpredictable future environments. The level of inbreeding was relatively low across the study populations although the assessment of the inbreeding level should be done every five years to determine any unfavourable change in inbreeding levels, so that appropriate steps can be taken. The population structure analysis in the study revealed some signals of admixture and genetic relationship between Afrikaner, Nguni, Drakensberger and Bonsmara. Nguni cattle shared some genetic links with the Afrikaner cattle, with about 8% of its genome derived from the Afrikaner cattle.   This result may reflect co-ancestry regarding the origin of these breeds as both these came from the same migration route into Southern Africa (Scholtz, 2011).

On the other hand, the Bonsmara cattle shared limited genetic links (0.5%) with Afrikaner cattle, which was unexpected. This low relationship may be attributed to genetic drift or a small sample size. Information generated from this study forms the basis for future management of these cattle breeds. The effective population size appeared to have decreased in all the study breeds in recent generations. The lower effective population sizes for the Afrikaner, Angus and Holstein breeds compared to those of Nguni, Bonsmara and Drakensberger at more recent generations, could be due to intense selection, inbreeding and probably wide spread use of artificial insemination in South Africa and the use of relatively few elite sires after 1970 (Hayes et al., 1990). In order to maximise the net response in genetic gain, Food and Agricultural Organisation (FAO) (FAO 1998) recommended an effective population size of 50 per generation. The Afrikaner, Angus and Holstein were below the FAO recommended number.

This suggested that these breeds are endangered and close to critical stage therefore pointing out the need for implementation of appropriate conservation programs as well as new selection and breeding strategies to ensure long-term fitness of these breeds. These could include increasing the number of animals contributing offspring to each generation by increasing the cow populations. It is critical for food security and rural development because it allows farmers to select stock or develop new breeds in response to changing conditions, including climate change, new or resurgent disease threats, new knowledge of human nutritional requirements, and changing market conditions or societal needs (FAO, 2010).

A total of 47 genomic regions were identified including genes associated with immune response, reproductive performances, coat colour, tropical adaptation and nervous system were identified. For example, the keratin family and one heat shock protein in the Nguni cattle were associated with tropical adaptation. In addition to the role that the keratin genes play during epidermis development, they also play a role in the formation of the hair shaft (Wu et al., 2008). Skin colour and the thickness of hair directly influence the thermos-resistance of cattle living in the tropics. Nguni cattle have smoother and shinier hair coats compared to European cattle breeds. These characteristics provide Nguni cattle with a greater ability to regulate body temperature and to more efficiently maintain cellular function during heat as well as the ability to resist tick infestation (Marufu et al., 2009).

Several candidate genes directly or indirectly involved in reproductive pathways including oestrus process, ovulation rate, testis development and prostaglandin were found. The fact that the Afrikaner, Nguni, Drakensberger and Bonsmara cattle have the ability to produce and reproduce under harsh environment conditions and are considered excellent dam lines for crossbreeding (Scholtz, 2010), supports the strong selection on reproductive loci that is likely to have occurred in their adaptation to South African conditions. Genes involved in muscle organ development and skeleton development were also identified as being under selection in the Bonsmara and Afrikaner cattle populations. The results presented in the study forms the basis for effective management of South African cattle breeds. Furthermore, a genomic understanding of how and where natural selection has shaped the pattern of genetic variation among cattle breeds in SA was unveiled by identifying loci that are important to the development of SA cattle breeds.

Future studies should focus on expanding the breed level analysis through the inclusion of all major African cattle breeds (Gautier et al., 2009) together with cattle breeds of the world. This could further provide insight with regard to the genetic relationship shared among South African cattle breeds and cattle breeds of the world and shed more light on the genomic requirement for survival in African environments.

Please contact the Primary Researcher if you need a copy of the comprehensive report of this project – Pranisha Soma on pranisha@arc.agric.za

Epitope mapping of two heartwater proteins

Epitope mapping of two heartwater proteins – Sheep and Cattle

Epitope mapping of two heartwater proteins and identification of vaccine components to be included in the multi-epitope DNA vaccine

Industry Sector: Cattle and Small Stock

Research focus area: Unlocking the Potential of Red Meat through commercialization and technology transfer

Research Institute: Agricultural Research Council Onderstepoort Veterinary Institute (ARC-OVI) University of Pretoria (UP)

Researcher: Dr Ivy Sebatjane PhD

Research Team:

Title Initials Surname Highest Qualification
Dr Mirinda van Kleef PhD
Dr A Pretorius PhD
Dr H Steyn Dtech
Ms N Thema MSc

Final report approved: 2015

Aims of the project

  • To formulate an effective attenuated heartwater vaccine for cattle witch is easy to administer
  • To determine the optimum dose and route of attenuated Welgevonden vaccine in Holstein cattle
  • To determine duration of immunity
  • To field challenge the immunized cattle in a heartwater endemic region

Executive Summary

Heartwater is caused by the organism Ehrlichia ruminantium which is transmitted by ticks of the Amblyomma species. It affects mainly domestic and wild ruminants and it is controlled by use of a live blood vaccine. Alternative vaccines are required due to the limitations associated with the current vaccine. At ARC-OVI research towards alternative vaccines has been ongoing and one example is the use of DNA vaccines.

Previous studies has shown that the DNA vaccines could offer protection in the laboratory but failed in the field where the disease is transmitted by ticks. In this project we investigated the use of a multi-epitope DNA vaccine which is made up of short sequences from different antigens that were shown to be immunogenic.

After three inoculations with the multi-epitope DNA vaccine delivered by i.m. injection and the gene gun, none of the sheep survived challenge with E. ruminantium infected ticks. However, when the same multi-epitope DNA vaccine was formulated with an adjuvant, it protected three of the five sheep against tick transmitted E. ruminantium infection.

From this project we learnt that when using subunit vaccines like DNA vaccines, it is very important to include appropriate adjuvants in the vaccine formulation in order to improve the immunogenicity of the DNA vaccine

Please contact the Primary Researcher if you need a copy of the comprehensive report of this project – Ivy Sebatjane on sebatjanei@arc.agric.za