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Fmd control strategies in kerala

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  • 1. FOOT-AND-MOUTH DISEASE: IMPLEMENTING AN EFFECTIVE DISEASE CONTROL PROGRAMS AND ROLE OF NSP ANTIBODY TESTING V I Bishor and Faisal Siyavudeen ubio Biotechnology Systems Pvt. Ltd Technology Incubation Center, Kinfra Hitech Park, Kalamassery, Kerala, India. Foot and Mouth disease: Overview Foot and Mouth Disease (FMD) is a severe, highly contagious viral disease of livestock with significant economic impact. The disease causes severe production losses and while the majority of affected animals recover, the disease often leaves them weakened and debilitated, with severe reduction in milk production. In a susceptible population, morbidity approaches 100% and intensively reared animals are more susceptible to the disease than traditional breeds. While the disease is rarely fatal in adult animals, there is high mortality in young animals due to myocarditis or by lack of milk when the dam is infected by the disease. Because of the huge economic impact, FMD is enlisted in the World Organisation for Animal Health (OIE) Terrestrial Animal Health Code, 2009, and world-wide guidelines are in place for detection and control of the disease. FMD virus is found in all excretions and secretions from an infected animal. The virus may be present in milk and semen for up to 4 days before the animal shows clinical signs of disease. Infected animals notably breathe out a large amount of aerosolized virus, which can infect other animals via the respiratory or oral routes. All these factors make the virus spread very fast among populations. Animals that have recovered from infection also serve as carriers of the virus. The key elements the strategy for dealing with FMD are early detection, warning, and prevention. These include continuous monitoring of FMD occurrence and prevalence, and characterisation of FMD viruses. Protection of FMD- free areas should be enhanced with stringent controls and surveillance on import and cross-border animal movement. The recommended control measures include controlling introduction of new animals to existing stock, monitoring and immediate reporting of illness and sound bio-security practices at farm level. According to OIE, A good FMD surveillance system should be under the responsibility of the Government Veterinary Authority, as is done in Kerala today. A procedure should be in place for rapid collection and transport of samples, and subsequent testing and diagnosis. This would ensure that disease occurrence is detected as soon as possible, and quarantine measures initiated quickly to avoid outbreaks. The surveillance systems should also include an early warning system throughout the production, marketing and processing chain for reporting suspicious cases. Farmers and workers who have day- today contact with livestock, veterinarians and other technical staff should report promptly any suspicion of FMD. They should be supported directly or indirectly (e.g. through private veterinarians or veterinary para-professionals) through government information programmes and the Veterinary Authority. All suspect cases of FMD should
  • 2. be investigated immediately. Where suspicion cannot be resolved by epidemiological and clinical investigation, samples should be taken and tested immediately. The surveillance program should also implement regular and frequent clinical inspection and serological testing of high-risk groups of animals, such as those adjacent to an FMD infected area. Foot and Mouth Disease Control in Kerala Kerala’s Animal Disease Control Project (ADCP) is lauded as the model for the entire country. The vaccination program conducted as part of ADCP has led to significant reduction in the occurrence of FMD in the state. Continuous monitoring and re- vaccinations have kept the disease away from the state for years altogether. However, we have seen increased incidence of FMD outbreaks in recent years and this points to new influential factors that have come into play. These factors include: 1. Increased movement of slaughter animals into the state across the border without any control. 2. Introduction of new dairy animals from infected areas into the state, especially as part of government programs targeted at ensuring increase of livestock population. 3. Lack of continuous disease monitoring among livestock populations in the state that slows down outbreak detection, emergency response and epidemic prevention. The FMD control program has to be refined by incorporating control measures that consider these new factors, so that we sustain and improve the FMD disease status across the state. FMD Disease control in Kerala: Proposed measures. The following measures are to be implemented to refine the FMD disease control program in Kerala. 1. Clinical Surveillance 2. Migration Control and Monitoring* 3. Control of cross-border livestock trade 4. Early detection measures and epidemic control Clinical surveillance Even though we have implemented a successful routine vaccination program, we do not have a continuous monitoring system to identify virus circulation or silent carriers in the population. A major outbreak is often followed by a series of smaller outbreaks caused by previously infected carriers, and lack of identification of such carriers makes epidemic control less effective. To mitigate these risks, a separate monitoring program should be put in place in addition to the vaccination efficacy screening. Such a program would involve: 1. Regular random sampling of serum from across the state 2. Testing the sample for the presence of infection 3. Identification of infected carriers or new infections 4. Quarantine and control measures including emergency vaccination Migration Control and Monitoring The State Government provides financial incentives for purchase of new livestock animals under various schemes. However, these incentives have been utilized more for intra-state trade, without any increase in livestock population. To ensure that financial
  • 3. incentives result in increased livestock populations, the government has started insisting that such incentives will be available only for import of animals from other states. While this is a welcome development from a demographical point of view, it has a serious negative impact on disease control programs. Most areas adjoining our state have higher incidence of FMD with less developed disease control systems, there is a high chance that FMD carriers may be imported through inter-state purchase of new dairy animals. A program where every new dairy animal imported into the state under government schemes has to be tested and certified free of FMD before the purchase is made has to be considered. Control of Cross-Border livestock trade. The number of slaughter animals imported into the state through our border check- posts is huge. These animals do not mingle with local livestock, and they spend just a few hours in the state before they are slaughtered, which makes the risk of infections from these animals lesser in a general sense. However, this does not hold for FMD, as the disease is so contagious that even animals that live near the road through which infected animals are transported are at risk of infection. As the number of slaughter animals imported is large, the cumulative risk is very high. In fact, there is strong suspicion that the recent outbreaks at various places in Kerala were caused by infected slaughter animals. A screening program may be implemented at border check-posts to screen and exclude infected animals. Ideally, every animal should be checked for infection and the physical or financial responsibility to dispose of the infected animal should be fixed on the importer. The tagging system at the check-posts should be extended to retain test data and associate it with individual animals. A good vigilance program that randomly screens animals at slaughter-houses can then ensure accountability and assure efficacy of the screening program by cross-checking results from the check-post. Early detection measures and epidemic control Emergency response is a critical part of epidemic control. Today, treatment is focused on areas where outbreaks are reported, and treatment often follows the spreading outbreak. However, the most difficult aspect of an epidemic is its fast spread which makes control problematic, and more attention must be given to containment. By the time an FMD infection is detected in an animal, the disease would be incubating in all the animals in direct contact with the infected animal. The most important step in FMD epidemic control is to quickly establish an infection perimeter. Today, this perimeter is established empirically. We propose that all susceptible animals in infected and adjoining areas and areas with high risk of contagion be screened to identify early infections whenever an epidemic is reported. This data should be used to establish the infection perimeter quickly and accurately. This perimeter should then be used to implement quarantine measures in the infected area, and emergency vaccination should be performed around the perimeter to block spread, as is done today. Of course, this should be followed by intensive supportive therapy for infected animals, thereby containing the outbreak quickly. Once the epidemic is over, all the animals in the area should be screened again for the presence of carriers so that follow-up outbreaks do not occur.
  • 4. FMD control measures: implementing Challenges. While the control measures proposed above can lead to vast improvements in our FMD control program, there are specific challenges that must be overcome before they can be effectively implemented. A clinical surveillance scheme that aims to detect silent FMD carriers cannot rely on clinical examination, and would require laboratory diagnosis. Today, the basic laboratory facility for FMD diagnosis is available only at one centre in Kerala – the CDIO/IAH&VB labs at Palode. It is not practical for daily random samples to be sent to a single center within the state. The sample management problem cannot be solved even if district-wide diagnosis facilities are established, as considerable manpower would be required for serum transport and lab analysis. This option would also entail high capital expenditure in the form of additional equipment for serum handling, storage and lab analysis. Migration control and monitoring programs that require ‘FMD-free’ certification of dairy animals before purchase would need a testing method, which would allow the veterinary doctor to test the animal at the point of purchase. It is not possible for the doctor to collect the serum of the animal to be purchased, then send it to a lab for testing and close the deal after the result is available, as the turnaround time will be in days. A mobile lab that accompanies the doctor is one option, but the cost is prohibitive. Similar challenges also exist for check-post screening. A typical animal carriage vehicle will spend 30-45 minutes at the check-post for animal tagging and clearance. It is impossible to screen all the animals in the carriage within this time using conventional methods. Serum collection and off-site lab diagnosis is not an option here, as infected animals would have carried the infection into the state by the time the results are available. In the case of disease screening to establish infection perimeters, quick results are very important as the disease spreads by the minute. A 2-3 day delay in obtaining results would make the test data almost useless as the disease perimeter would have morphed and expanded by that time. In all these measures, it is important to make sure that vaccinated, non-infected animals are not judged as infected by looking at the presence of FMD antibodies in their serum, and that vaccinated silent carriers are identified. Screening of antibodies of Non structural protein is a simple way of differentiating the infected and vaccinated animals. NSP antibodies can be monitored by Enzyme Linked Immunosorbent assay technique. A recently introduced lateral flow assay test for NSP antibodies offers much easier and portable way of screening these antibodies in bovine serum sample. Rapid FMD NSP Testing All the FMD control measures outlined above involve fast, reliable, de-centralized screening of the disease. The implementation challenges outlined in the previous section can be used to derive a set of requirements for the ideal diagnostic technique to be used in the FMD disease screening. They are: 1. Quick results should available in just a few minutes. 2. Should require no instrumentation, instruments should be portable if present. 3. Should be easy to use. 4. Should allow decentralized implementation (should not require serum transport)
  • 5. 5. Should require no, or low, capital expenditure. 6. Should be able to execute the test and read result in the field itself. 7. Should not require refrigerated storage. 8. Should differentiate between vaccinated and infected animals. The only diagnostic technique available today that satisfies these requirements for FMD diagnosis is the FMD Non-structural-protein (NSP) rapid lateral flow assay. Various FMD control measures can be effectively implemented by using this kind of assay for screening. Assay Overview and Usage Rapid FMD NSP test (available as ‘ubio quickVET FMD NSP’) uses recombinant FMD NSP antigens and monoclonal antibodies to detect the disease. Antibodies to NSP antigen are present only at the time of infection, and these antibodies are not type-specific. Hence, the presence of these antibodies indicates the presence of FMD infection, irrespective of the virus type. FMD NSP rapid test is designed so that even a technician with limited expertise can perform the test easily. The veterinarian or the technician draws blood from the animal using a syringe or a vacutainer, optionally coated with a clot-activator for faster serum separation. The syringe is kept till the serum separates, and then, 3 drops of serum are added to the sample hole on the test card using a dropper. The results can be read in just 5-10 minutes. After the test is complete and result recorded, the used kits should be disposed of according to standard disposal procedure followed for clinical specimens in veterinary hospitals and labs. Conclusion Kerala’s FMD control program can be refined and disease outbreaks can be prevented by implementing effective screening programs. These programs require easy, rapid tests which can be executed on site, without access to lab facilities. FMD NSP lateral flow assay provides a perfect tool that would allow us to implement such screening programs Efficiently thus making the state FMD free. Address for correspondence Dr. V I Bishor. Phone: +91 9744122269, e mail: bishor@ubio.in