Bluetongue and keeping it at bay
According to the World Organisation for Animal Health
Bluetongue is an infectious, non-contagious, vector-borne viral disease that affects wild and domestic ruminants such as sheep, goats, cattle, buffaloes, deer, most species of African antelope and camels. Infection with bluetongue virus is inapparent in the vast majority of animals but can cause fatal disease in a proportion of infected sheep, deer and wild ruminants. Insect vector of just a few species in the genus Culicoides transmit bluetongue virus among susceptible ruminants, having become infected by feeding on viraemic animals. Twenty-six different serotypes have been identified and the ability of each strain to cause disease varies considerably. There is no public-health risk associated with bluetongue as the virus is not transmitted through contact with animals or wool, or through consumption of milk. Vaccination is used as the most effective and practical measure to minimise losses related to the disease and to potentially interrupt the cycle from infected animal to vector along with insect control measures.
Teagasc's recent National Beef Conference took place in Carrick-on-Shannon, a heartland of drystock production. While the conference agenda ranged across several topical subjects, the presentation and discussion around bluetongue disease was particularly timely and informative, writes Matt O’Keeffe
The viral disease which can infect cattle, sheep, goats, deer and minor species such as alpacas, has travelled across northwestern Europe and has been detected in eastern and central England. There is a distinct possibility that it has already spread as far as Wales and is now dormant as temperatures restrict insect movement at this time of year. There is a significant risk that the midge-borne virus could make the leap across the Irish sea, either on the wind or carried by various vectors including animal, vehicular and people movements. Wintertime, with low temperatures, provides a respite from its entry, as the midge population is inactive, allowing us to reinforce our disease defence protocols against the prospect of the infection reaching our shores.
At the conference, Dr Eoin Ryan, who is senior superintending veterinary inspector at the Department of Agriculture, Food and the Marine (DAFM), and head of the DAFM’s National Disease Control Centre, presented a comprehensive analysis of the disease. He explored its impact on animals, and the biggest risk factors for Irish livestock.
Bluetongue can only be transmitted by midges infecting animals through biting one infected animal and then infecting another through a subsequent biting action. Insect vector of just a few species in the genus Culicoides transmit the virus. There is no respiratory, faecal, or other animal-to-animal direct infection vector. However, apart from the potential for these species arriving on an easterly wind, there are several other potential means of spread, as Dr Ryan explained. We already have midges of the species present in Ireland, but it’s the disease itself which must be kept out so that subsequent virus carriage by midges from animal to animal is avoided.
Preventative measures
Dr Ryan listed imported livestock, semen or embryos as potential risk factors to be avoided. The National Disease Control Centre at the DAFM is providing strong advice around preventative measures that can reduce the risk of bluetongue infecting our herds and flocks. These include not importing cattle or other vulnerable animals into the country. At the very least, if animals are imported, the DAFM’s advice is to comply with the strict rules in place around livestock imports to minimise the risk of the disease being introduced. While EU regulations prevent outright bans on these imports, it is clearly in our interests to minimise this risk factor. Likewise, the strong advice is not to import semen or embryos into Ireland. Our island status provides some degree of protection, provided the voluntary compliance with the DAFM’s advice is followed. As things stand, there are controls in place to minimise spread through livestock importation. The import of live ruminants from Britain to the island of Ireland, for instance, is suspended, while germinal products can only be imported where animal-health requirements for bluetongue can be fully certified. Likewise, there are restrictions in place regarding imports from fellow EU states. These are only permitted where detailed certification requirements are satisfied.
Economic and welfare impacts
Bluetongue virus infection in Irish herds and flocks would have serious impacts on animal health and welfare, and Dr Ryan highlighted the fact that there are potential implications for live animal and germinal products - including ova, semen and embryos - being exported from Ireland, if bluetongue disease is detected here. While there are already significant challenges to our calf export trade to the continent, for example, an outbreak of bluetongue, however limited, would be a serious setback to this trade.
Inevitability
Currently, Ireland is the only country in Europe that has not succumbed to some level of bluetongue in its livestock population. There are two ways of looking at this. Either we regard it as an inevitability that the disease will eventually arrive, or we take every possible precaution to prevent its introduction and protect our Bluetongue-free status, with all the benefits that delivers for animal health and our livestock exports. While there are no human health or food-safety implications from Bluetongue, its impacts on animal health and farmers’ economic welfare are considerable. The clinical outcomes include fever, loss of appetite, reduced milk yield, and, in particularly vulnerable species such as sheep, high mortality rates. Farmers need to inform themselves of the physical infection signs in order to act quickly if infection is suspected, as we go into the warmer Spring and summer months. An abundance of caution is required as the potential tell-tale signs of bluetongue infection are also similar to other infections such as infectious bovine rhinotracheitis and catarrhal fever.
Controlling pneumonia in suckler wealings
The single most infectious disease challenge in suckler weanlings is pneumonia. That was the message delivered at Teagasc’s National Beef Conference. The warning coincided with the period when animals are most vulnerable to stress-related infections with the weaning, farm-to-farm movement, mart sales and housing of weanlings across the country, but it is a warning that can have application at any time of the year regarding bovine respiratory disease infection. Dr John Donlon of Teagasc Grange provided the lead at the Beef Conference in terms of advice aimed at prevention, control and vaccination protocols around pneumonia management. As mentioned above, reducing stress at critical times is singularly important. The provision of concentrates prior to and after weaning is important as animals move from a milk-rich diet to a grass, silage and concentrate one. Gradual weaning is advised as is regular monitoring for clinical signs of the disease. Early treatment is essential if the most extreme outcomes of pneumonia infection are to be avoided. Teagasc advice includes reference to the value of vaccination against respiratory disease infection, provided it is part of a comprehensive overall health plan. It should be said that pneumonia is not a disease solely related to suckler weanlings as any advisor, researcher, vet or farmer will know and acknowledge. Neither is it confined to specific periods, housing or environmental conditions. The disease vectors include viruses as well as bacteria, and a respiratory challenge can often be the result of a multi-faceted attack. Poor nutrition, overcrowded housing and poor weather conditions, while not directly responsible for respiratory disease infection, nevertheless leave animals far more vulnerable. As ever, vaccination has a role, but it is not an antidote to poor animal management. While prevention is always better than cure, the management of pneumonia is a critical aspect of livestock management.