Controlling Scabby Mouth in the Live Sheep Trade

Transcription

1 final report Project code: IVE.101 Prepared by: RT Norris and DC Moir Agriculture Western Australia Date published: May 2000 ISBN: PUBISHED BY Meat & ivestock Australia imited ocked Bag 991 NORTH SYDNEY NSW 2059 Controlling Scabby Mouth in the ive Sheep Trade Meat & ivestock Australia acknowledges the matching funds provided by the Australian Government to support the research and development detailed in this publication. This publication is published by Meat & ivestock Australia imited ABN (MA). Care is taken to ensure the accuracy of the information contained in this publication. However MA cannot accept responsibility for the accuracy or completeness of the information or opinions contained in the publication. You should make your own enquiries before making decisions concerning your interests. Reproduction in whole or in part of this publication is prohibited without prior written consent of MA.

2 Project Background Controlling Scabby Mouth in the ive Sheep Trade IVE.101 Final Report to Meat & ivestock Australia Agriculture Western Australia 22May, 2000 The live sheep export industry provides significant income for the Australian agricultural sector. The live sheep trade accounts for around 13% of the annual national sheep turn off and returns in excess of $150 million annually to the national economy. Australia banned exports of Jive sheep to Saudi Arabia in 1990 following repeated rejections by that country, ostensibly because of high levels of scabby mouth disease. Before the ban, Saudi Arabia was the main market for Australian sheep taking 45% of the 6-7 million sheep exported live annually. The rejections were widely publicised in the national and international media. The publicity adversely affected Australia's international reputation, not just regarding our livestock in the Middle East region but also for non agricultural products both in the region and in other. areas of the world. No sheep have been sent directly to Saudi Arabia in the last 10 years except for a one-off shipment in 1995 which was also "rejected" by the Saudis because of high levels of scabby mouth. In 1996, complaints about high levels of scabby mouth in Australian sheep were received from Jordan and the United Arab Emirates, which had become major markets for our sheep. In many shipments, 40-60% of sheep were affected and rejections were threatened. Scabby mouth is a common disease found in all sheep-raising countries. The disease rarely causes problems of economic significance in Australia, and is usually not observed by producers. Consequently, most producers considered that their flocks were free of the disease and preventive action was rarely undertaken in Australia, particularly in Western Australia. Humans can be infected with the virus and there was widespread fear of the disease both from the human health aspects and because of concerns about introducing infection to supposedly clean flocks. However, many producers began vaccinating at lamb marking in 1997 following a large extension campaign in Western Australia called "Sqatch to catch the market". From a base of only a few thousand doses of vaccine used before the campaign, an estimated 5 million doses were used in 1997 and more than 7 million doses in J ~.~,..-o-::'''~- Agriculture Western Australia has initiated a significant research program in support of the extension campaign. This has involved close collaboration with various sectors of the live sheep trade, including producers, exporters, shippers and Neil Buchanan in the Middle East. The research shows that scabby mouth prevalence in sheep on arrival in the Middle East has fallen from 40-60% before the campaign to 6-10% in Although there has been considerable success in controlling scabby mouth during live export, there are two areas requiring further investigation. First, a small but significant number of producers are reluctant to use the vaccine because they consider a) that their property is virus free and do not wish to introduce the live virus with the vaccine orb) that vaccinating all lambs

3 I r ~ _ I gre.;~ at marking time is not justified when they sell only a relatively small number of sheep for live export. However, many of these producers may be willing to use the vaccine if it could be used within a few days before trucking from the farm to the pre-embarkation feedlot. The second area requiring investigation is to establish the effectiveness of the new CS vaccine applicator in controlling scabby mouth during live export. Previous research has shown that the prevalence can vary widely between farm groups of sheep (0% up to 23% in vaccinated sheep) on arrival in the Middle East. It is known that earlier models of the vaccine applicator did not deliver an accurate dose of vaccine to each sheep and it is postulated that under-dosing may be the main reason for the wide variation in prevalence. Other reasons include poor vaccination technique and loss of immunity between lamb marking and export several months later. Field testing of the new applicator indicates that it delivers an accurate dose of vaccine, however the variation in prevalence of scabby mouth after using the new applicator has not been established. Potential Industry Benefit Controlling scabby mouth in the live sheep trade from Australia would eliminate a significant threat to the future of this strategically important industry. In addition, evidence that Australia can deliver sheep with consistently less than 5% scabby mouth on arrival in the Middle East opens the possibility of resuming direct trade with Saudi Arabia. The proposed scabby mouth vaccination program for Saudi Arabia is based on two vaccinations; one at lamb marking time with a second vaccination at least two weeks before trucking from the farm. However, a small study in June 1999 suggested that a single vaccination a few days before trucking from the farm may be effective in controlling scabby mouth (Appendix 1). If confirmed, such an option would significantly reduce vaccination costs for the Saudi Arabian market and would also provide another alternative for producers who are currently reluctant to use the vaccine at lamb marking. The study in June was conducted outside the time of year when scabby mouth levels are usually highest (February-May) and involved only 8 farm groups of sheep. It is proposed to undertake further research during the high risk period and to involve a much greater number of farm groups of sheep. It is also important to establish the effectiveness of the new CS vaccine applicator in controlling scabby mouth and in minimising the variation in prevalence between farm groups of sheep. ow levels of scabby mouth with little variation between farm groups would indicate that under-dosing and not poor technique or loss of immunity was the main reason for unsatisfactory control of the disease previously. Good control with the new applicator may eliminate the need for a second vaccination before trucking for the Saudi market and would assist in overall efforts to control the disease during export to all markets in the region. Objectives By June 2000 to: 1. Establish the effectiveness of a single vaccination, given either a few days before trucking or on the day of trucking to the feedlot, in controlling scabby mouth in the live sheep trade. 2. Establish the effectiveness of the new CS vaccine applicator in controlling scabby mouth in the live sheep trade. Methodology The proposed methodology is described below: a) Pre-trucking study -2-

4 ~ ~ :,( Farm groups of sheep will be selected ive.101 for study - Controlling after purchase Scabby for Mouth live export in the ive by a Sheep commercial Trade buyer, providing they have not previously been vaccinated against scabby mouth. On each farm, 150 young sheep will be divided randomly into 3 treatment groups and given an ear tag: a) vaccinated 7-10 days before trucking to the feedlot; b) vaccinated within 24 hours before trucking; c) controls not vaccinated. It is anticipated that between 10 and 20 farm groups of young sheep will be selected for each of two studies conducted between February and May Autumn is the time of the year when scabby mouth is considered to be at highest levels. After arrival in a commercial feedlot in the Middle East, the trial sheep will be examined individually by Neil Buchanan and scored for the presence of scabby mouth lesions. Although the design is relatively simple, there are considerable logistical difficulties in selecting the farms and in complying with the commercial constraints of the live sheep trade. For these reasons, a group of AGWEST officers will need to be on standby in various locations throughout the sheep raising areas of Western Australia. With minimal notice, they will be expected to contact the producer, arrange to visit the property and apply the various treatments. In some cases, the officers will need to re-visit properties to vaccinate the sheep in treatment b) above. b) Monitoring study Farm groups of sheep will be selected on arrival at a pre-embarkation feedlot on two occasions between February and May 2000 (avoiding the study described above). Approximately 50 sheep per group from about 20 farms will be selected on each occasion providing they are identifiable to a farm (it is anticipated that some groups will need to be given an ear tag at the feedlot). The sheep will be examined individually for scabby mouth by Neil Buchanan after arrival in a commercial feedlot in the Middle East. The previous owner of the sheep will be interviewed by telephone to determine whether the sheep were vaccinated previously and if so, whether the new CS vaccine applicator was used. Dissemination Strategy A report will be prepared after the completion of all four studies and distributed to produc.er groups in Western Australia, live sheep exporters, MA and ivecorp. The results will also be extended to sheep producers by way of AGWEST's Agricultural Memo, rural newspapers, seminars and radio talks. The information will also be made available to sheep producers and exporters in other areas of Australia. Results Pre-trucking study Unfortunately, it was not possible to complete the pre-trucking study, despite several attempts. Regular contact was made with all of the sheep exporters from Western Australia between February and May in an attempt to find suitable young sheep for the study. However, it proved extremely difficult to find un-vaccinated lambs eligible for selection. The success of the vaccination campaign in Western Australia has resulted in relatively few un-vaccinated flocks being available. Also, consignments of lambs exported have been relatively small recently, largely because of low numbers of suitable sheep for export from Western Australia. Nevertheless, the findings of a study undertaken in 1999 (Appendix 1), together with other research where vaccination was given shortly before trucking from the farm, provide some confidence that vaccination shortly before leaving the farm will effectively control scabby mouth during sea transport. Consequently, it is doubtful whether further research on the effectiveness of pre-trucking vaccination is necessary. However, if further research is -3-

5 r.,. ~' considered necessary, it should not be undertaken in Western Australia because of the difficulties discussed above. Monitoring study When a potentially suitable voyage was identified in the first half of 2000, the pte-trucking study was given priority. However, when it became clear that the pre-trucking study could not be undertaken for the selected voyage, the monitoring study was attempted. On one occasion this work had to be abandoned because of competing priorities at the feedlot (simultaneous receivals for two shipments and loading for a third shipment). Despite these difficulties, the work was finally undertaken in April, and a report is attached at Appendix 2. Communications The report of the monitoring study (Appendix 2) has been widely distributed to AGWEST veterinarians for production of extension articles in the Agency's Agricultural Memos. The report has also been distributed to exporters in Western Australia, the state's producer groups (W AFF & PGA), ive Corp, senior policy officers in A... FFA, Tony Brightling and Neil Buchanan. Additional extension will be undertaken from time to time, to maintain the momentum of the scabby mouth vaccination campaign in Western Australia, and support will be provided to producers, exporters and others elsewhere in Australia as required. Conclusions A considerable body of knowledge both from the present project and from previous research clearly indicates that scabby mouth can be controlled effectively during live export of sheep to the Middle East. ination is the most effective means of controlling scabby mouth in the live sheep trade. The cooperation of all sectors of the trade is essential for the success of a large scale vaccination campaign such as that which has operated in Western Australia in recent years. A single vaccination at lamb marking has resulted in low levels (4% to 10%) of scabby mouth at discharge in the Middle East. ination shortly before leaving the farm is effective in controlling scabby mouth, but is less convenient for most producers than vaccination at lamb marking. Two vaccinations, with the second vaccination given shortly before export, has resulted in negligible levels (less than 0.5%) of scabby mouth at discharge. Scabby mouth is no longer considered an issue of concern in most markets for Australian sheep in the Middle East. Budget report A final budget report is not available at present but is expected to be submitted to MA in July

6 _ ~ 1' Background Prevalence of scabby mouth after pre-trucking vaccination Don Moir*, Richard Norris*, Neil Buchanant and Greg Norman* * Agricultw-e W A, t Meat & ivestock Australia 23 June, 1999 Appendix 1 Management strategies are under investigation to ensure sheep consistently have less than 5% prevalence of scabby mouth on arrival in the Middle East. Two studies late in 1997 showed scabby mouth prevalences of 9.2% and 6.5% in lambs vaccinated at marking about 5 months previously, compared to 41.2% in unvaccinated controls. A study in April 1998 examined whether a booster vaccinaiion, given on entry to the feedlot before export, affected the level of scabby mouth on arrival in the Middle East. The results (Norris eta! 1998) showed that the booster vaccination significantly reduced the level of scabby mouth; young sheep that received the booster had a prevalence of 2.9% compared to 8.0% in controls that had been vaccinated at marking only. In a repeat of this study in June 1998, lambs that received a booster vaccination at the feedlot had less than 5% scabby mouth in the Middle East compared to 9.8% in the controls. Some sheep in this study were not previously vaccinated, so their booster vaccination was actually a primary vaccination. This group also had less than 5% scabby mouth in the Middle East. Ideally, vaccination against scabby mouth should be given at least 14 days before challenge to allow sufficient time for immunity to develop. However, most sheep for live export are purchased less than 14 days before trucking to the feedlot. Consequently, there was a need to examine the effectiveness of vaccinating at times that are more convenient for those involved in the live sheep trade. The present study was carried out to determine whether a primary vaccination given either within two weeks of trucking from the farm or within 24 hours before trucking would achieve less than 5% clinical scabby mouth at discharge in the Middle East. Method Sheep that were purchased for live export in May 1999 were selected for study if they were not previously vaccinated against scabby mouth. On each of eight properties, drop merino lambs were randomly allocated to three treatment groups of 50 lambs per group and given a coloured ear tag. The treatment groups were: vaccinated against scabby mouth from 4 to 11 days before trucking from the farm (Orange tags); vaccinated within 24 hours before trucking (Blue tags); not vaccinated (Pink tags). In most flocks vaccination was carried out by the farmer (flocks 2 and 18 were vaccinated by AGWEST officers), either on the bare skin around the tail or behind the elbow, using the new Scabigard (CS) applicator. The trial animals were mixed with the rest of the export consignment on each farm until arrival at the feedlot when :J.!I trial animals from all farms were grouped and penned separately. The sheep were loaded on a ship at Fremantle after 2 to 4 days in the feedlot and arrived in Jordan 16 days later. After arrival at a feedlot in Jordan, the trial sheep were examined for scabby mouth by an Australian veterinarian and scored for lesion severity using the following system (0 =no scabby -5-

7 _ l t' mouth; 1 =mild lesions not readily seen; 2!arger lesions easily detected; 3 =extensive readily visible lesions). Some trial sheep were mixed with the rest of the consignment in the feedlot in Western Australia or during loading onto the ship and were lost to followup. Other trial sheep could not be correctly identified to farm group because of errors in reading or recording the ear tag number in the feedlot in Jordan. These sheep were allocated to flock "99". Differences between treatment groups were compared using the Chi-squared test. Results The prevalence of scabby mouth (score 2 & 3 lesions) was 0.3% in the group vaccinated 4 to 11 days before trucking, 1.9% in the group vaccinated within 24 hours of of trucking, and 12.1% in the control group (P<0.01, Table 1). The prevalence of scabby mouth was not significantly different between the two vaccinated groups. The prevalence of scabby mouth iii controls was 10% or higher in seven out of the eight flocks. In contrast, the prevalence of scabby mouth was greater than 10% in only one flock group that was vaccinated (11.1 %, flock 2 vaccinated on the day of trucking). In all other flocks that were vaccinated, the prevalence was below 5.0%. Table 1 Numbers of lambs per flock in vaccination (pre trucking and day of trucking) and control groups and number and percent with noticeable scabby mouth lesions (score 2 & 3) in each group. Pre-trucking Day of trucking Control Flock No. 2+3 % No. 2+3 % No. 2+3 % ll Total Discussion Not all sheep were available for examination il) the Middle East, some having been lost to followup between leaving the farm and arrival at the feedlot in Jordan. However, there were similar numbers of sheep between treatment groups. It is likely that any bias was small and that similar results would have been obtained had the sheep not been lost to follow up. The results indicate that both vaccination strategies were successful in reducing the prevalence of scabby mouth at discharge in the Middle East to less than the target of 5%. The finding of 10% or more scabby mouth in the control flocks indicates that there was significant exposure to the disease during the export process. The virtual absence of scabby mouth in the pre-trucking group suggests that there may be a benefit in allowing time for immunity to develop before sheep enter the export process. However, some farm groups were vaccinated only a few days before tmcking from the farm. In -6- ~

8 r r l ' l~ addition, sheep vaccinated within 24 hours of trucking also had very little clinical scabby mouth and the level was not significantly different to the pre-trucking group. These findings indicate that vaccination close to or on the day of trucking may proyide good protection against scabby mouth during live export. The timing of vaccination in the pre-trucking group was less than 14 days before leaving the farm. Although vaccination should be given at least 14 days before challenge, 12 days was the longest period between purchase of the sheep and trucking from the farm. This reflects.the reality of the live sheep trade where buyers may purchase sheep up to the day of trucking to the feedlot. Such a short time between purchase and trucking from the farm limits the desired timing of vaccination given current buying practices for live export. The present study involved a small number of farms in Western Australia with relatively small numbers of sheep. Ideally the study should be repeated, preferably during the late summerautumn period when scabby mouth levels are known to be high on arrival in the Middle East. If similar results are obtained then vaccination close to or on the day of trucking could be considered for adoption to control scabby mouth during live export. This would provide another vaccination option that would be more convenient than current strategies for many producers. The results of this study provide further evidence that Australian sheep can be delivered to overseas markets with consistently less than 5% scabby mouth. References Norris R, Moir D, Buchanan Nand Norman G (1998): Report on "Prevalence of scabby mouth after booster vaccination", Agriculture Western Australia (12 May 1998) Norris R, Moir D, Buchanan Nand Norman G (1998): Report on "Prevalence of scabby mouth after booster vaccination: Report of second trial", Agriculture Western Australia (8 July 1998) ~ _ -7-

9 l Scabby mouth prevalence after on-farm vaccination Richard Norris*, Neil Buchanant, Don Moir*, Michael Johns* and Greg Norman* *Agriculture W A, t Meat & ivestock Australia Appendix 2 17 May, 2000 Background Previous studies have shown that vaccination against scabby mouth is the most effective way of controlling the disease in sheep during export to the Middle East. amb marking is the preferred time for vaccination on commercial farms. Two studies late in 1997 showed scabby mouth prevalences of 9.2% and 6.5% in the Middle East in lambs vaccinated at marking about 5 months previously, compared to about 40% in unvaccinated lambs. It was postulated that under-dosing may have been an important factor contributing to higherthan-expected levels of scabby mouth in some farm groups of lambs (up to 23% observed). It was reported that the number of lambs vaccinated per bottle was frequently 50% or more greater than the number of doses provided per bottle, using the vaccinator available at that time. Consequently, a new applicator was developed to deliver a more-accurate dose of vaccine, and was widely used at lamb marking in The present study was undertaken to examine the level of scabby mouth that is observed in lambs exported from Western Australia to the Middle East, following vaccination on commercial farms. Methods The study involved a commercial shipment of lambs exported from Fremantle to Kuwait in April Twenty three farm groups of lambs that were born in 1999 were selected on arrival at a pre-embarkation feedlot if they already contained an ear tag to identify the property of origin. They were followed through to Kuwait where they were individually examined for scabby mouth in the feedlot days later. Scabby mouth lesions were scored by an Australian veterinarian using the following system: 0 = no scabby mouth; 1 =mild lesions not readily seen; 2 larger lesions easily detected; 3 = extensive readily visible lesions. Officers of Agriculture W A subsequently telephoned the owner/manager of each farm group of lambs, and asked a series of questions about the vaccination history of the lambs. Results The number of lambs in each farm group, and the number with scabby mouth are shown in Table 1. The prevalence of noticeable lesions of scabby mouth (score 2 & 3) was 3.97% in the entire group. All farm groups were vaccinated except Flock 5. Of the 22 farm groups that were vaccinated, 17 used the new Scabigard (CS) applicator. The three fa1m groups with the highest levels of scabby mouth were vaccinated with the new applicator. Flocks 1 & 3 were vaccinated by the same mulesing contractor. -8-

10 l l...; Table 1 Numbers of Iambs in each farm group, and numbers with varying levels of scabby mouth, prevalence of noticeable lesions, and vaccination status. Flock ambs Scabby Mouth Score No No --~0~--~----~~~--~~~~--~ Total Prevalence (%) Total ~~J. :'7~7c:"",":;~ ~-- Discussion ,864 1, ination Status No New Applicator Both Unsure No No Although the overall level of scabby mouth was less than 5%, it was disappointing that high levels (10-20%) were seen in some flocks vaccinated with the new applicator. It is widely considered that the new applicator is accurate: under-dosing was not an issue in 1999, and there was no suggestion of under-dosing at interview of the owners in this study. Consequently, other factors besides under-dosing have probably contributed to the high levels of scabby mouth in some farm groups of lambs. The present study was not designed to investigate these factors. The target level of scabby mouth for Saudi Arabia is less than 5% in all shipments. The finding that the overall level of scabby mouth was 4% in the present study should provide much comfort for regulatory authorities and others involved in the live sheep trade. Although not strictly representative of all lambs exported from Western Australia recently, the present study strongly suggests that a single vaccination at lamb marking combined with the new applicator will result in very low levels of scabby mouth in the Middle East. Additional vaccination closer to the time of export will provide added confidence that the target can be met consistently. Negligible levels have been seen in shipments to Saudi Arabia so far, supporting this proposition. -9-