High-risk months for redwater

Vets are reporting a higher incidence than normal of tick-borne diseases in 2024.

Cavan-based vet Finbarr Kiernan told the Irish Farmers Journal that tick-borne diseases often occur where farmers rent or buy land that has previously been under-grazed.

The high grasses and rough vegetation provide the ideal breeding ground for ticks, particularly when combined with warm and moist weather conditions.

“The season for tick problems is usually May to September but not limited to that if the conditions are right,” said Kiernan.

The rising popularity of organic farming and environmental schemes has meant that some farmers are spreading a lot less fertiliser and topping fields is being restricted until later in the year on some options in ACRES. This has meant there is more rough grazing available to harbour ticks.

“We have a situation in the northwest where some farmers housed cattle in September and they are only getting back out in the last two weeks to graze land again. There’s a dense mat of grass on some farms which can be ideal conditions for ticks, so we are seeing more cases this year compared to others,” Kiernan added

Redwater or babesiosis is caused by the parasite Babesia divergens, which is carried by ticks. Early signs of redwater include animals staying away from the herd on their own, reduced appetite, a hollow left flank, high temperature, frothy urine with a red-brownish colour and thin diarrhoea.

In the later stages, the animal will become weak and stagger, the colour of skin and mucous membranes will change from pink to pale or yellow.

It will become constipated and die.

In Ireland, there are certain parts of the country and certain land types which have ticks on them.

Some farmers in the west would even be aware of particular fields on their farm being prone to animals getting redwater when grazing them. The ticks transfer the parasite into the blood of cattle when they feed on them.

The parasite attacks and destroys red blood cells in cattle, hence the name redwater, and this is where the damaged red blood cells are passed in urine, giving it a darkened appearance.

The tick population

With the tick being key to transmitting the disease, we must look at where tick populations are. The tick goes through three stages of development over four to six years, starting as an egg, to larvae, to nymph, and finally to an adult.

Each time, it needs a blood feed to develop to the next stage. It will actually latch on to a host like cattle for three to 10 days and feed.

When a tick is infected, it will spread this parasite through the feeding activity at all stages.

Cattle usually won’t show symptoms for three to four weeks after this exposure to the tick. The parasite babesia enters the blood and will attack red blood cells that carry oxygen. This is why we see the symptoms listed below.

The ticks themselves like wet, damp conditions and are active in late spring and early autumn. However, this has changed with reported cases later and earlier each year.

The tick also likes a certain habitat, which can be rougher grazing ground, but this doesn’t mean you can’t find ticks in ordinary grasslands.

Generally, they like the shade and don’t like direct heat or sunlight for long periods.

There is a very important factor with redwater and that is young animals in tick areas will have very good immunity against the disease up to nine months of age.

In fact, young animals before six months will generally not get redwater, as it affects older stock mainly. This is why animals in certain areas rarely succumb to the disease, but bought-in stock with no exposure pose a massive risk.

Older stock can get the disease but, usually, it is animals that have been brought into a tick area with redwater, that have no previous exposure.

There are two stages to the disease. Early on, the disease requires careful observation to pick it up. The value of at least one daily walk through stock to pick up symptoms is key.

Early symptoms

Later symptoms

Vet intervention is a must if redwater is suspected to prevent death. Once an animal has been diagnosed, usually by the symptoms as described above, your vet can give medicine to treat these cases. This product is known as imidocarb or Imizol.

Some later spotted cases will require blood transfusion, as the red blood cells are too low. This is why these animals are weak. The parasite has attacked and destroyed the red blood cells which carry oxygen around the body.

People handling animals need to be very careful with anaemic cattle, they can be very unpredictable and sometimes dangerous. High stress can also cause death.

The vet will usually take blood for the transfusion from an older animal like a mature cow. These treated animals need careful handling and monitoring for the following 48 to 72 hours.

Reducing exposure to ticks is one way of preventing the disease. This is very difficult but anywhere that rough ground is reclaimed makes it less tick-friendly. With most cattle in tick areas having some resistance, we can assume they are low-risk but good herding is still required.

Spot-on products will give three to four weeks cover where animals are grazing high-risk areas. These treatments often require repeat applications during the high-risk periods.

Other diseases

Cattle ticks can carry other diseases so the spot-on treatments are important where high levels of ticks are seen. The imidocarb dipropionate product (Imizol) can also be used to prevent redwater. Follow the instructions on the product for dose rate and timing.

This protection only lasts four weeks and also has very long withdrawals of 21 days for milk and 218 days for meat. This is very important where summer-grazing animals are due to be slaughtered at the end of the grazing season.

This is not a vaccination and will only last for four weeks.

Any bought-in cattle that are going to graze tick areas should be treated before turnout, when ticks are active and should have a spot-on treatment as well.