THE DREADED EAST COAST FEVER
Riphicephalus appendiculatus – the brown-ear tick (discussed in part II) transmits Anaplasmosis but, and more importantly, is the primary vector of East Coast fever (ECF). ECF has an incubation period of between 10 and 25 days with death occurring between 18 to 30 days.
In herds that have had no exposure to ECF, mortality can be as high as 100%.
ECF is a lethal disease said to be directly responsible for the loss of about 1,5 million cattle in the sub-region every year. This translates to a staggering economic loss to cattle farmers. And it is a loss that African farmers must fight to overcome.
The parasite responsible for ECF, Theileria parva, is a highly adapted protozoal parasite with a unique penetrating mechanism.
Simply put, the tick bites your cow, the parasite enters the host animal through the tick’s saliva and quickly begins its deadly work. Before you know what’s happening your animal is dead.
Often, by the time, you see the clinical signs of ECF it’s too late for treatment. And even early treatment may not work.
Animals that live after they have been deliberately, or naturally, infected with T. parva become carriers. This is a major problem that compounds the difficulty of controlling ECF because the carriers are a source of future possible infection.
SYMPTOMS OF EAST COAST FEVER
The ‘sick’ tick may keep the (T. parva) parasite alive for up to two years, on the ground. The parasite infects a tick feeding on an infected, or a carrier, animal. Infected ticks then pass the disease on to disease-free cattle; typically, this would happen when animals are under some kind of pressure; after calving, during a drought or a shortage of feed and when they are suffering another illness.
The first signs of ECF are listlessness and standing apart from the group. Fever develops within seven to ten days and rectal temperatures of 40°C and more must be seen as cause for alarm.
Other signs are enlarged lymph nodes (see drawing to check position), going off feed, a milky eye and white gums, nasal discharge, possibly diarrhea, and difficulty with breathing which becomes more severe as the disease progresses.
Some animals may turn around and around and become paralysed, a sign of brain damage.
The first lymph gland to swell is usually the parotid gland in front of the ear since the brown ear ticks tend to attach in the ear. The swollen glands can be seen and felt, quite easily.
A dipping programme is essential. Some vets advise dipping once a week to protect cattle from ECF. Since mortality from ECF is 100% in European cattle this would certainly be required for such herds. African type cattle are just as vulnerable if they are moved from an ECF free area to an area where ECF is endemic (constantly occurring).
The drugs Buparvaquone and Parvaquone are highly effective against protozoal parasites. If the disease is spotted early on and the animal is injected, with either Buparvaquone or Parvaquone, the temperature drops to normal within two days and the parasite populations are rapidly reduced.
Treating early is the key to saving the animal but is not a guarantee.
Injecting with long-acting tetracycline stops the parasites from developing. This is more or less ‘blocking’ cattle against ECF.
If you want to send animals to pasture known to have had ECF previously, inject with long-acting tetracycline a month before opening the gate.
Many of the tetracycline drugs are suspended in an oily base which can pool in the tissue – so remember to massage and make sure the drug is dispersed.
INFECT AND TREAT
There is a live vaccine for ECF (referred to in the literature as the Muguga vaccine) which comes with an oxytetracycline antibiotic. The vaccine is injected (subcutaneously) and the animal is treated with an oxytetracycline at the same time. This is known as the infection and treatment method (ITM). Cattle may show mild signs of ECF but these will pass.
According to some sources, certain animals will not survive infection despite the simultaneous use of oxytetracycline. However, once they have survived infection, either in the veldt or through injection with live vaccine, they develop a strong immunity which they retain for life.
Naturally, they will be carriers, so bringing in animals from other herds, or regions, comes with a risk. Travelling is stressful for cattle and stress weakens the immune system. Common sense will tell you that these animals will be highly vulnerable to ECF.
Do not move animals from ECF-free to ECF-endemic areas or the other way around. Bear in mind that global warming is extending the range of many of the ticks which poses a further threat to cattle.
Make a habit of constantly thinking things through before acting if you want to keep your cattle and grow your herds.
There is no mother to calf immunity, so vaccinate your calves after they are a month old, and never before that.
Don’t vaccinate animals after they are six months in-calf, if they have poor body condition, if they are sick or if they are being used to work.
The vaccine is not cheap and only approved technicians and vets can vaccinate. Group power is a clear option here. It makes things easier for small-scale cattlemen and women if they can form groups to buy the vaccine and get the technicians out to vaccinate their herds.
Never see ECF protection through live vaccine as an excuse to stop dipping. There are a number of tick-borne parasites from which your cattle need protection.