doi:10.5455/vetworld.2013.558-562 Investigation of caprine arthritis-encephalitis virus in Sudan using competitive enzyme-linked immunosorbent assay

Aim: This seroprevalence study was carried out to detect anti Caprine Arthritis-Encephalitis Virus (CAEV) antibodies in goat sera in five States in Sudan during 2009 and 2010. Materials and Methods: In this study, 432 sera samples collected from five States in Sudan were screened for anti-CAEV antibodies using a commercially available competitive ELISA (cELISA) kit. Results: Out of 432 samples, 25 (5.8%) tested positive using ELISA. The highest prevalence was recorded in El-Gazira State (19%), whereas the prevalence was 10.7% in Kassala State, 0.92% in Khartoum State and no samples tested positive from Northern and River Nile States. Conclusion: Our findings revealed that the disease had spread to other states, apart from its previously known prevalence in Khartoum, in Sudan. Our results call for better control and quarantine measures on imports of live animals into Sudan for genetic improvement programs. Further epizootiological investigations on CAEV in goats and Maedi Visna Virus in sheep at a national level are also needed to carefully monitor and prevent its spread and also to determine its impact on the economy of Sudan.


Introduction
CAEV strains), but it has been clearly demonstrated that cross-species infection occurs naturally with other Small ruminant lentiviruses (SRLVs) comprise variants [10].Caprine Arthritis-Encephalitis Virus (CAEV) of goats Following infection, animals produce anti-viral and Maedi Visna Virus (MVV) of sheep [1].These antibodies, although seroconversion may occur any retroviruses cause chronic inflammatory disease that time requiring few weeks to several months [11].The affects brain, lungs, joints, and mammary glands primary cells infected in vivo are monocytes and causing considerable economic losses and reduced macrophages, with the bone marrow serving as a animal production and welfare worldwide [2].CAEV reservoir for the infection [12].Virus is disseminated to is an RNA virus that belongs to the genus Lentivirus the target tissues via the blood stream by localizing (family-Retroviridae) that includes non-oncogenic within the monocytes.exogenous viruses that cause various diseases of Diagnosis of SRLV infections can be made based mammals [3].CAEV was first identified and described on clinical signs.However, this is often not feasible in 1980 in the USA [4,5] Transmission of CAEV occurs because only a small proportion of the infected animals primarily by ingestion of infected colostrum or milk or exhibit clear clinical signs.Disease is rarely observed through respiratory tract.Horizontal transmission has before the age of two years except in the case of kids of been registered as a result of close contact, even in goats where encephalitis can become evident within animals maintain on pasture [6], but whether or not few months of infection [13].However, the period vertical transmission occurs is still unclear [7].Viral from infection to the development of symptoms transmission between goats and sheep has been (latency period) often ranges from several months to reported [8,9] according to the manufacturer's instructions to detect Until recently there was no solid evidence that antibodies against the CAEV envelope glycoprotein, CAEV infection represents a threat to small ruminants gp135.The test is based on the principle of competitive in Sudan.However, a recent study [15], documented ELISA in which serum antibody to CAEV in the serious health problems confined to only Saanen breed sample inhibits the binding of horseradish peroxidase of goats that were imported for genetic improvement.
(HRP)-labeled CAEV-specific monoclonal antibody to These problems included arthritis, mastitis and CAEV antigen coated to the plates.Binding of the pneumonia in adult goats and encephalitis in kids.
HRP-labeled monoclonal antibody conjugate is However, no data are available regarding the status of detected by the addition of enzyme substrate and CAEV infection in states other than Khartoum and in quantified by subsequent color product development.other breeds of goats.
Weak color development due to inhibition of the Thus, the goal of the present study was to determine monoclonal antibody binding to the antigen coated to the seroprevalence of CAEV infection among goats in the plates indicates the presence of CAEV antibodies in other regions of Sudan and among other breeds of the sample sera.The degree of inhibition is expressed goats.We strongly believe that significant findings from as percent inhibition (PI) and is calculated as follows: our study will contribute to designing effective strategies  Nile states (Table -1).may also apply to a high percentage of the infections After the adjustment for test misclassification, the found in Shami breed in Kassala (10.7%) which were recently imported from Cyprus.true overall prevalence of the CAEV in this study was As mentioned earlier, only a few of the infected 5.3%, while in El-Gazira, Kassla and Khartoum States animals develop clinical signs and therefore the risks it was 18.4%, 10.2% and 0.42%, respectively.
posed by the disease are usually underestimated by the Regarding the breeds of the sampled goats, 24 owners and veterinary clinicians.Almost all veterinarians (19%) out of 126 samples from Shami breed were we interacted with did not hear nor had no knowledge found positive and one sample from Saanen crossabout this disease.On the other hand, the negative breed was positive (0.92%), while all the samples from results in the River Nile state in purebred saanen and indigenous goat breeds were negative (Table 2 and 3).
their crossbred lines may indicate the presence of Discussion disease-free animals, due to the recent rigorous regulations imposed by the veterinary authorities of Earlier surveys in Africa documented the that state.However, because of delayed seroconversion, evidence for SRLVs infections in Kenya [18], Morocco some of the infected animals may test positive in the [19], Nigeria [20], Mozambique [21] and Algeria [22].
future.On the other hand, our finding that the positive An interesting factor that was common to these reports samples were detected in Khartoum state in Saanen is that all these countries imported animals from crossbred goats is in agreement with the results obtained Europe which facilitated the introduction and spread of by Elfahal et al. [15] who reported the prevalence of the the disease.This highlights the fact that the spread of disease in the same ecotype.

SRLVs occurred predominantly via importation of
It is worth noting that all animals that were animals [22,23].Further evidence for such a mode of confirmed as positives with CAEV were maintained spread of the infection comes from previous studied under a closed management system which may have which showed that in Japan [24] and Mexico [25], contributed to the horizontal transmission when the CAEV was found in goats that were imported for their infected animals are introduced; a notion supported by genetic improvement programs.However, animals that the findings of East et al.
[31] and Gufler [6,32].carry the virus may not show any clinical signs because Fortunately, no CAEV infections have so far been of a delayed seroconversion.Such serological latency detected in the indigenous Nubian goats in Sudan, may often require several months [26] or years before clearly indicating that the risk of infection is largely seroconversion becomes evident or may never occur at associated with importing infected animals.Majority all, which is a prominent feature of SRLV infections of the indigenous goats are reared on open natural [11,27,28,29].Animals may also fail to develop pastures where chances of horizontal transmission are antibody levels that can be detected by commonly used minimal.However, this situation may be altered if the serology tests [11,30].
management system is shifted to a closed system; often Recently in Sudan, the concerned veterinary to cater to the requirements of exports to neighboring authorities started regulating the imports of goats for countries.genetic improvement programmes by allowing only Significant findings from our study clearly the import/introduction of animals that were brought suggest that proper control measures are needed to from flocks certified free of the disease.However, as prevent future occurrences of clinical outbreaks caused discussed above, animals that carry the virus may not by CAEV infections in goat herds of Sudan.show any clinical signs complicating the task of the Furthermore, we strongly believe that the information officials involved in the import and control obtained on seroprevalence of CAEV infection in this programmes.Indeed, the disease was confirmed in study is an important first step towards the Sudan in 2010 in goat herds in Khartoum State [15], establishment of effective control and/or eradication where all the positive reactors were either imported programmes in the future.from other countries or were crossbred.
Goats that tested positive by cELISA were from

Conclusion
El-Gazira (19%), Kassala (10.7%), and Khartoum Key findings from our study clearly showed that (0.92%) states and no antibodies were detected in goats CAEV infection exists in other states in Sudan besides from Northern and River Nile States.All reactors in El-Khartoum, albeit currently being restricted to imported Gazira and Kassala States belong to the Shami breed of breeds and their crosses.Furthermore, based on our goats.The high seropositivity of antibodies in Elfindings, we strongly believe that there is an urgent Gazira State (19%) clearly indicated an importation of need for detailed epizootiological investigations on infected animals into the state.The same reasoning and goats: chronic pneumonia leukoencephalitis and and drafted the manuscript.KMT, DAS, RHH arthritis.Rev. Infect.Dis., 7: 89-98.14.Knowles, D. and Herrmann, L. M. (2008) Caprine arthritis collected the samples and analyzed the data.ZAM and -encephalitis & Maedi-Visna.In: OIE Biological Standards AME contributed to the conception and design of the Commission (Ed.), Manual of Diagnostic Tests and Vaccines study and thoroughly revised the manuscript.All for Terrestrial Animals (Mammals, Birds, and Bees), vol.2, authors read and approved the final manuscript.6th edition.World organization for Animal Health (OIE), pp.983-991, Chapter 2. 7. 3/4.

Table - 1
. Seropositivity to CAEV antibodies in goats detected by cELISA from different states in Sudan

Table - 2
. Seropositivity to CAEV infection in goats breeds detected by cELISA from different states in Sudan

Table - 3
. CAEV Seropositivity in goat breeds detected by cELISA Koptopoulos, G. (2006) Development of a semi-nested PCRCAEV and Maedi Visna virus at the national level to using degenerate primers for the generic detection of small monitor its spread and determine its impact on the ruminant lentiviruses proviral DNA.J. Virol., 135: 240-246.economy of Sudan.We also recommend that better 12. Gendelman, H. E., Narayan, O., Molineaux, S., Clements, J. control and quarantine measures be implemented while E. and Ghotbi, Z. (1985) Slow, persistent replication of lentiviruses: Role of tissue macrophages and macrophage importing animals for genetic improvement.precursors in bone marrow.Proc.Natl.Acad.Sci., USA 82: Authors' contributions 7086-7090.13.Narayan, O. and Cork, L.(1985) Lentiviral diseases of sheep AME, MOH and KAE carried out the ELISA assays