At the 2022 Official Vet (OV) Conference, hosted by Improve International in collaboration with the Animal and Plant Health Agency (APHA), infectious diseases took the spotlight, with infections such as African swine fever (ASF), West Nile virus, rabies, avian influenza (AI) and more being discussed by specialist speakers.
During her opening address, the Chief Veterinary Officer (CVO), Christine Middlemiss, reminded delegates that there has been no break in the incidences of AI in the past year: for staff, there has been “no escape”, and she thanked everyone involved. For those who receive email notifications of outbreaks, inboxes are bulging. All are reminded that the virus is not zoonotic, but handling dead birds, including the recent spate of seabirds, should be avoided by the public.
An overview of the disease-related issues in the UK includes managing the rabies risk from the pets of Ukrainian refugees. The value of pets in supporting traumatised families is fully recognised, and risk assessments involve a “huge amount of work”. Bovine tuberculosis (bTB) continues to be a major area of focus as efforts move towards eradication. The new EU animal health law is being addressed so that exports can be achieved and difficulties overcome. Monkeypox has highlighted the role of One Health in protecting both animals and people; the One Health approach is very much live, not just being talked about.
An increasing incidence of non-compliant pet certificates is troublesome, and more details are to follow from a review of the importation of domestic pets
An increasing incidence of non-compliant pet certificates is troublesome, and more details are to follow from a review of the importation of domestic pets. The Office International des Epizooties (OIE) has now become the World Organisation for Animal Health (WOAH), but the aims remain the same. The CVO also acknowledged the increasing value of the OV’s role in recognising and managing disease and the workload involved.
The first presentation was by Luke Gamble, the CEO of Mission Rabies. He explained that the work to control rabies in dogs is achieving a direct reduction in human rabies. As such, veterinary surgeons and nurses are being encouraged to volunteer for task forces in the next major thrust in Cambodia. Veterinary practices are invited to sponsor a member of staff to combat the “world’s deadliest zoonotic disease”.
Dogs and children are the principal victims of rabies, and the disease affects the “poorest of the poor”. It costs the equivalent of 51 days’ wages to purchase a human vaccine in Africa. The official estimate is that a child dies from rabies every nine minutes, but due to his direct experience with Mission Rabies, Luke believes this is a gross underestimation. He highlights that in rural areas there is a cost to families if someone dies in hospital. If death is imminent, the person is collected and taken back to the village, so no official record of the cause of death is available.
The results of the charity’s vaccination programme are impressive. After activity in Goa, for example, there have been no human deaths for four years, and the incidence in dogs has dropped from 10.6 to 0.2 cases per month. The charity has vaccinated 2 million dogs and educated 5 million people on how to avoid bites and the value of washing a wound with iodine. Their targets are high but achievable, with 80 percent of schools having education sessions and 70 percent of dogs vaccinated in an area through owners bringing dogs to the team’s location and catching teams locating feral animals. GPS technology is also being used to provide datasets, and post-vaccination surveys provide evidence, which is essential to achieve government engagement. Oral bait vaccines, which have been described as “a game changer”, are under development.
With rabies recognised in 159 countries, there is a lot of dedicated work to do, but some area administrators are realising that their people can be a final rabies generation.
Bats, foxes and final thoughts
Helen Roberts (Exotic Diseases Control Team, APHA) indicated that there are 17 recognised species of lyssavirus that have bats as the reservoir animal. The UK is free of the “classic” rabies, with western Europe showing a good improvement year-by-year, but the disease is still common in eastern Europe. However, the majority of cared-for pets in Ukraine are vaccinated and well. Oral vaccination, delivered by aircraft or by hand, has been shown to be successful in foxes.
The UK is free of the “classic” rabies, with western Europe showing a good improvement year-by-year, but the disease is still common in eastern Europe
The virus is spread by saliva, not by faeces, urine or blood. Following a bite, it can take weeks or even months for the virus to reach the brain and then the saliva glands. But death occurs rapidly after acute clinical signs. It is recognised that human rabies is “very frightening for people”.
Although the UK has officially been free of bluetongue since 2011, following the 2007 outbreak, passive clinical and active laboratory surveillance is ongoing. Sampling of cattle takes place in November and December (the end of the vector season) at the time of a TB test. In her presentation, Christina Papadopoulou highlighted the risks of airborne introduction from midges and imported animals. New strains are appearing in Europe, and some 10,000 samples from imported animals are taken each year. Any positive animals are isolated, culled or returned. A risk of incursion tool is applied, and enhanced surveillance takes place in the south and east of England.
African swine fever in wild boar
Europe is experiencing a surge of ASF (Asfarviridae) cases. Raquel Jorquera indicated that people walking in the countryside can help by photographing and reporting dead boars to the Defra Rural Helpline. Forestry England rangers are primed to report any sightings, increase public awareness and distribute information posters. In healthy populations, it is expected that 10 percent of wild boars die each year, and only 10 percent of those are ever found, usually at forest edges.
In healthy populations, it is expected that 10 percent of wild boars die each year, and only 10 percent of those are ever found, usually at forest edges
Samples from hunted boar in Europe show lower levels of virus detection than from found dead pigs. In the UK, submissions of dead pigs have all been negative to date, but humans are responsible for the spread of ASF. People therefore need to be alert and behave responsibly. One precaution against spreading ASF is to avoid leaving cooked meat leftovers after picnics as the virus survives the cooking process. Transmission of the virus is by direct contact and through ticks and feed. A vaccine is awaited.
West Nile virus
Climate change and an increase in the mosquito population (Culex spp.) found in the UK are enhancing the risk of West Nile fever (flavivirus) in horses. Valentina Vitale explained that infected horses usually have mild symptoms with no fever. Infected horses are not contagious, but the virus can be transferred from mare to foal in milk.
An inactivated vaccine (lineage 1 strain) is available in the UK with an annual booster. A mobile app, EquiBioSafe, provides useful information on the virus. The disease is notifiable, but there is no active surveillance in the UK. Vector surveillance of mosquitos and wild birds is ongoing, and where an infected vector population is suspected, control of mosquito levels at dawn and dusk is recommended.
Disease monitoring and avian influenza
Information is constantly assembled from all over the world, looking for new, emerging or deteriorating disease situations. Paul Gale provided interesting insights into the production of the weekly reports that guide public and veterinary health authorities. International disease monitoring uses a risk of disease incursion tool, and the assessments are published online. Maps showing the progression of identified diseases are also available.
With the current HPA1H5 incursion, it is anticipated that migratory birds will be returning to the UK from infected areas. For much of 2022, the link between poultry disease and wild birds was decoupled but has now been re-established. It is anticipated that more cases will arise in the UK, and housing orders for poultry are likely. Housing needs to be done early to be effective. Some raptors, including sparrowhawks, are known to be infected. Vaccination of poultry is being considered throughout Europe, including the UK. Detailed analysis is available from the government website.
Lesley Larkin, a veterinary surgeon in the UK Health Security Agency, outlined the public health perspective of Salmonella. Some 10,000 cases of gastrointestinal symptoms are reported in humans each year, but the total is estimated at 50,000 afflicted. The main sources of the disease are sewage and contaminated food, with cases linked to sources such as poultry, meat, eggs, salad, fruit and nuts. Salmonella is not a problem limited to meat eaters, but the warm meat supply chain requires risk reduction.
Outbreaks have been traced to contaminated sheep and cattle premises, and the high number of animal movements is an issue. The example of nine infected farms (DT104) led to 73 linked premises, including slaughterhouses, retail outlets and catering. Over 26,000 animal movements were recorded, resulting in 800 human cases. Dogs can be asymptomatic carriers, and isolates from dogs have been linked to human cases, with raw pet food a source of concern. The application of whole genome sequencing is improving the ability to detect and better understand human/animal pathogens.
A comprehensive review of bTB included policy updates for England, Wales and Scotland, as well as for badger vaccination and the investigation of TB incidents. Pilar Romero explained that a 7 percent drop in new herd incidences was recorded for England, but there was no change in the herd prevalence in high-risk areas. The identification of Mycobacterium bovis from tissue samples is now available within three weeks using PCR.
Field trials of a cattle vaccine are due to be completed by the end of 2023, with marketing authorisation to be sought. Validation for trade of vaccinated cattle by the WOAH is anticipated in 2025. In annually tested edge areas, post-movement testing is planned for 2023. The involvement of extra measures by farmers and vets is due to be incorporated into a British Cattle Veterinary Association training scheme starting in February 2023. The information gained from planned initiatives, including those in Sussex and Oxfordshire, will add relevant understanding of the disease. The TB Hub is the prime source of updated information.
Dave Harris indicated a falling incidence of disease in the high TB areas in Wales; however, clusters of positive herds are a problem that is being addressed. Mandatory pre-movement testing, severe interpretation of skin tests, increased use of gamma tests and additional blood testing of herds with bought-in cattle are being applied. As has been found with other testing initiatives, the more investigations, the greater the level of disease found. Routine skin testing is leaving behind infected animals on some farms. So far, the approved lay tester proof of concept trial has been successful, with general acceptance by the farming community. Change to compensation allowances is due, and a refreshed TB programme is to be published.
Jenni Diffin reminded delegates that although Scotland is officially TB free, this applies to indigenous cattle only – in 2021, there were seven confirmed new breakdowns. Cattle bought in from the high-risk areas of England are pre- and post-movement tested, with enhanced slaughterhouse inspections. However, 60 percent of herds in Scotland are not routinely tested for TB, and many herds are reared for slaughter only.
It is proposed that failure to isolate reactors and inconclusive reactors will result in reduced compensation, as a pre-movement test result is to be valid for 30 days, not 60, and there will be a penalty for unclean cattle at slaughter. Consultation with farmers and vets has ended, and the resulting changes are due to come into play from the end of 2022. There is no recognised wildlife reservoir of M. bovis in Scotland.
Results of badger vaccination
Zara Gerrard detailed the results of various badger vaccination trials. Intramuscularly vaccinated communities of badgers show a reduction in infection in both vaccinated and unvaccinated animals. A herd immunity effect has been recorded, and vaccinated dams pass immunity to cubs. Only one third of the adults need to be vaccinated to provide community immunity.
Intramuscularly vaccinated communities of badgers show a reduction in infection in both vaccinated and unvaccinated animals
Comparisons between culling and vaccination indicate that the reduction of disease is roughly equal. Studies of oral dosing of anaesthetised badgers in Ireland expect that only 30 percent of badgers need to be dosed to provide population immunity. The policy is now to phase out badger culling and increase vaccination. To facilitate more vaccinations, veterinary surgeons need a licence and training to capture, inject and mark a badger.
An ongoing survey will help to direct future information. It is expected that a reduction in TB-infected badgers will lead to a reduction of infection in cattle.
Research into TB positive herds
In 2021, some 2,500 TB-positive herds were investigated, and the details of this investigation were explained by Alison Hollingdale and Daisy Duncan at the conference. The investigated herds included herds persistently infected for 18 months, herds with 20 reactors, herds with no TB in the last five years, public access farms and a random selection. Known data was collected into a disease report form at a farm visit or over the telephone.
The report addresses TB biosecurity, the isolation of inconclusive reactors, public health risks, movement restrictions, potential risk pathways and the likely origin of infection. Addressed are three provisional risk pathways, six potential hazard options, 25 risk pathway options and four rankings. The aim of the report is to better understand TB at the farm, local, county and country level.
The home range of genotypes 11a, 17a and 25a helps identify disease movement. Information from the TB Advisory Service (TBAS), the interactive map (ibTB) and the interactive dashboard are incorporated into the TB Hub as an ongoing source of support for veterinary practices and their clients.
Farmers with TB-positive herds should be mindful of the human health risk from drinking unpasteurised milk, particularly for children
Andrew Carrington acted as chairman throughout the conference and fielded questions from delegates as part of a TB discussion on the forum. On the forum, it was clarified that the oral dosing of anaesthetised badgers was for a project only and that no oral vaccine for badgers is currently being worked on. Vaccination is seen as a means of protecting the gains achieved from culling, and a badger contraceptive is under consideration, but there are licensing issues.
Farmers with TB-positive herds should be mindful of the human health risk from drinking unpasteurised milk, particularly for children. The human BCG vaccine is available by request. It was also clarified that a faster reduction in cattle disease is needed if targeted bTB eradication is to be achieved.