Tick Prevention Week: What you need to know for livestock
What are ticks?
Ticks are obligate parasites, meaning they require a host to complete their lifecycle. They are of great veterinary and medical importance as they are only inferior to mosquitos in their disease spreading potential. Tick species feed on livestock and other animals around the world and are a diverse and successful group.
Tickborne agents can be mildly pathogenic, severely pathogenic and some can infect humans too. Additionally, ticks can also harm their hosts directly. Ticks can cause diseases such as tick paralysis and sweating sickness, by imparting tick-borne toxins in their saliva whilst taking a blood meal. Ticks may also cause skins wounds which may be infected, anaemia or even death.
The most common tick in the UK is Ixodes ricinus, which requires areas with lots of plant life and warmer temperatures generally meaning they begin to reappear in the spring. Tick infestations typically occur in woodland, heathland or rough ground with lots of vegetation.
Ticks can lead to several diseases and infections in cattle, by being vectors for infectious pathogens. The main pathogens of concern in UK cattle are Louping Ill virus, Anaplasma phagocytophilum and Babesia divergens. UK sheep are affected by Louping ill virus, Anaplasma Phagocytophilum (tickborne fever) and tick pyaemia.
Louping Ill virus causes louping ill, which is a fatal disease of the central nervous system, causing encephalitis (inflammation of the brain). This virus infects livestock and can also infect humans. This disease is spread by the tick Ixodes ricinus in the UK. Diagnosis is via neurological signs in combination with tick presence, and there are no specific treatments or vaccines for the virus.
The bacterium Anaplasma phagocytophilum gives rise to tickborne fever, and causes disease mainly in sheep but also cattle. Tickborne fever causes sudden fever and depression in sheep, and lowered milk yield and weight loss in cattle. Both animals may also suffer respiratory disease and abortion. There are no vaccines for tickborne fever and although suggested by clinical signs observed, it can only be diagnosed by PCR testing (looking for bacterial DNA). This disease is typically observed in young lambs or animals newly introduced to a tick-laden environment.
Tick pyaemia affects very young lambs already infected with A. phagocytophilum (tick-borne fever) and is caused by severe infection with Staphylococcus aureus. The infection results in abscesses leading to severe disability, lameness and even paralysis. Diagnosis can be confirmed by clinical signs, identification of bacteria and PCR, and it can be treated with antibiotics. The bacteria gain entry to the bloodstream when the tick Ixodes ricinus takes a blood meal, but can also be from infection of wounds and passed down in pregnancy. The main role of Ixodes ricinus here is vector transport of A. phagocytophilum as this enables conditions favourable to develop pyaemia. Importantly, tickborne fever can increase susceptibility to diseases such as louping ill, listeriosis, tick pyaemia and pneumonic pasteurellosis.
Babesiosis (Redwater Fever) is caused by infection with the Babesia protozoan parasite and is spread between cattle by the Ixodes tick in the UK. Babesia divergens typically causes babesiosis in cattle, but other Babesia species also infect sheep, goats, horses, pigs and dogs. Babesiosis occurs when these protozoan parasites infect red blood cells, ending in bursting of the cells. Babesiosis in cattle can cause diarrhoea, a temperature, red urine, increased heart rate and abortion. Death is rare in the UK.
Ticks become more active from early spring, through until temperatures drop in late autumn. It is important to remain more vigilant during this time period. Ticks spend most of their time away from the host, so are not easy to get rid of as they will reside in any moist, vegetation laden environment. Different geographic environments and vegetation can provide ecological niches for different tick species too.
You can apply the insecticide pyrethroid before possible exposure to ticks and during the animals’ exposure to act as a repellent. Through pasture improvement such as improving the draining to produce drier ground and removal of vegetation such as bushes and plants can reduce the tick population dramatically. This can be difficult if you use many pastures and rotate animals frequently.