Dipping, or acaricides, is one of the weapons in farmers’ arsenal in the war against East Coast fever (ECF). Here’s more on trade names and chemical groups.
The chemistry that dictates how acaricide compounds work is complex and needs profound levels of understanding.
Cattle farmers need only to know how the chemicals work as contact (on the skin) and systemic (in the system) tick poisons and repellents, how long the protection of the product lasts, and what the withdrawal periods are.
It is important to check on the toxicity of the specific dip you use and for this, I refer cattle farmers to a user chart compiled by Dr. Gerhard Verdoorn.
- Pyrethroid dips are non-systemic, which means that they do not enter the animal’s system but stay on the skin.
- They have a long residual effect (length of time the dip protects the animal against ticks) from 7 days in the rainy season to 15 days in the dry season.
- They are effective against tsetse fly.
- Pyrethroid dips can be conventionally used in dip tanks, spray races and backpack sprayers. They also come in pour-on formulations which are applied along the spine.
- The compound has an ingredient that ensures rapid spreading to the skin covering the rest of the body.
- Dairy farmers like to use pyrethroid dips because they leave virtually no residue in meat and milk and are safer to use. [Don’t confuse the residual effect of the dips with residue levels in meat and milk.]
- There is evidence that some populations of brown ear ticks have resistance to pyrethroids and organophosphates.
- A recent (January 2016) study undertaken in Uganda’s western and central corridor, by Ugandan and Japanese scientists, found alarming failure of pyrethroid and organophosphate dips.
- This resistance could be a problem in other sites across the sub region but there are also areas where the brown ear tick remains susceptible to pyrethroid dips.
Some trade names: Bayticol, Decatix, Bodyguard, Delete All, Ectoban, Maxipour.
- Organophosphate (OP) dips break down quickly in the environment but they are increasingly restricted because they are highly toxic to mammals, fish and birds.
- Although their use is not restricted in Africa – yet.
- OP acaricides are mostly used in combination with other dips, mainly pyrethroids, because of tick resistance that has developed during long use.
- The protective residual effect is around 4 days, and time from dipping to slaughter can vary from a week to two weeks depending on the specific type of compound used.
- OP compounds are not fussy about storage because they tolerate some degree of heat.
- They must be kept safely under lock and key like all chemicals but they don’t need cool storage facilities.
Some trade names: Supadip, Agridip, Bacdip, Corral.
- Amitraz, another non-systemic dip, is reported to be the most environmentally friendly acaricide.
- Sometimes called the tick detachment acaricide, amitraz kills the tick indirectly, by disrupting its life cycle.
- Ticks on the animal quickly detach after contact and fall to the ground.
- The speed at which the tick detaches makes it difficult, if not impossible, for the protozoa to enter the host cow.
- But amitraz has a residual life of 5 days and is not effective against the tsetse fly.
- It will wash off in the rain, so really it is no good in a rainy season in the tropics unless it is used in combination with a pyrethroid.
Some trade names: Amidip Max, Amitraz, Milbetraz, Taktic, Triatix.
- Fluazuron is a systemic (it reaches the ticks through the host’s blood) acaricide that acts by stopping the tick’s development – thus a tick development inhibitor, also called a growth inhibitor.
- Protection from the residual effect is 8 to 10 weeks and 6 weeks in the rainy season.
- Applied as a pour-on in 2 bands on either side of the animal’s spine, it is absorbed through the skin and by licking, and deposited in fat cells from where it is released, slowly, into the blood stream.
- Suckling calves don’t need treatment because they get enough fluazuron in their mothers’ milk, but lactating cows have a much shorter (4 to 6 weeks) protection time because of the excretion of fluazuron in the milk.
- Adults who have ingested Acatak with their blood meal lay eggs that are effectively dead. After they have fed and dropped off brown ear tick larvae and nymphs die when they try to move into the next stage of their life cycle (i.e. larvae to nymphs; nymphs to adults).
- Fluazuron (Acatak) is a good tick preventive that can work well if all the animals in a defined zone (for instance a farm, or a few farms, or a communal grazing area), are treated.
- The time to start applying Acatak is in early spring when the first batch of eggs hatch into larvae.
- In the tropics and moist sub-tropics, with up to 3 tick generations in a year, I would apply the pour-on as soon as the protection period was over.
- In the dry sub-tropics and further south, where ticks are seasonally active, three applications of Acatak in the tick season may be enough.
There are other types of compound used in acaricides, but information overload is not helpful. If any Africanfarming.com readers have used other dips with success please write to us.
Learning to manage and control ECF and its vector, the brown ear tick, is a work in progress. I would venture to say that it’s probably the most important job of the current time for cattle farmers, vets, animal health organisations, veterinary pharmaceutical companies, governments and agricultural journalists writing about cattle in Africa.