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Mitigation on tick resistance to acaricides

Tuesday, 22nd November 2016


Mitigation on tick resistance to acaricides

Question 1.What do acaricides do?


Answer: Acaricides are chemicals applied on the body of an animal to treat and protect it from external parasites especially ticks. When applied with proper guidance of a qualified veterinary professional, acaricides eliminate lice, fleas, tsetse flies, biting and nuisance flies and other ectoparasites that are common on animals.


Question 2. Are acaricides drugs?


Answer: According to the definition in the NDP/A Act, acaricides  are drugs and conform to the description of a drug as per the Act. 


Question 3. How do they aid improving animal health?


Answer: They improve animal health by protecting animals from pain and irritation from bites by ticks, lice, fleas, tsetse flies, biting and nuisance flies and other ecto parasites and flies, and prevention of diseases transmitted by the parasites (ticks and flies). 


Question 4. Of recent there claims of tick resistance on the performance of acaricides, what could be the problem?


Answer: Tick resistance to acaricides is a natural process, and is not new, because any living organism is capable of resisting anything that threatens it's existence. 

The recent episode of tick resistance to acaricides came to light in 2012, when most farmers were using acaricides in the class of Pyrethroids, against which resistance had been suspected and later confirmed. NDA came up with a programme to sensitise farmers and opinion leaders to change to another class of  acaricides as a short term measure pending consultation with other stake holders for medium and long term measures. 


More reasons for tick resistance include improper use of acaricide (irrational use); lack of proper gadgets for spraying; inadequate extension services; self-prescription of acaricides by farmers; prolonged use of one molecule of acaricide; mixing of different molecules of acaricides by farmers; under-dosing; among others.



Question 5. What measures has NDA done to mitigate the problem?


Answer: NDA has recommended removal of some classes of acaricides including combinations. Unfortunately consensus was not reached in time and meanwhile farmers out of desperation were interchanging acaricides and mixing them together resulting into multiple resistance to all the available acaricides which NDA predicted in 2013. 


The Authority has embarked on the following mitigation measures.

  -  carried out sensitisation to different stakeholders     

  -  Sampled available acaricides on the market and tested for quality

  -  Visited affected farm and picked ticks which have been tested for resistance and results given to farmers with possible solutions

  -  Prepared and sponsored a press release informing farmers and the general public on what to doIntensified surveillance in different parts of the country especially the most affected cattle corridor area

          -NDA sponsored a national wide study which is on-going to establish the extent of the resistance and its likely causes

         -NDA has engaged/ participated in several meeting with different stakeholders to formulate possible solutions


The situation now requires a completely new molecule that can be used for breaking the resistance. However the available new acaricide options all have limitations ranging from very long withdrawal periods to limited spectrum of action. I.e not effective on all ticks. 

The way forward is to use integrated methods of tick and tick borne diseases control that include: vaccination against East Coast fever, and withdrawal of most orall of the current acaricide classes. 


Concerted effort and inter-institutional effort and collaboration is needed to effect the identified interventions coupled with a clear framework for resistance monitoring. A policy on zoning of acaricide use is proposed but this would be built on a practical program to ensure uniform standard of acaricide application throughout the country and its enforcement by the MAAIF and local governments. 


Failure of proper planning and implementation of this programme will see the new acaricides also going to the waste in a short time, resulting into further decimation of the national herd. 


NDA is committed to finding a lasting solution to this problem. 


Question6. There some acaricides said to be effective but require a longer withdrawal period, and it seems farmers usually do not observe the period hence compromising the health of the population. What is your take if NDA is to safeguard the health of the population?

Withdrawal periods reflect the amount of time necessary for an animal to digest anad ministered product and the amount of time necessary for the product concentration level in the tissues (muscles) to decrease to a safe, acceptable level for consumption. When drug is administered on an animal there is a withdrawal period printed on the product label or package insert. Products carry meat withdrawal periods ranging from 0 to 60 days. Animals on treatment must be withheld from sale or slaughter during that period. Withdrawal times are not the same for all drugs. Milk produced during that period must be disposed of. In these situations or at any time a producer is uncertain of a specific drug withdrawal period, a veterinarian should be consulted.

Therefore, from the public health aspect it is challenging for farmers to observe the long prescribed withdraw periods for milk and meat. Like during this festive season where such products are on high demand, it is difficult fora farmer not to disposal off an animal or bird on treatment or milk for such a period.

This calls for concerted efforts of vigilance, not only from NDA, but many other stakeholders involvement like Ministry responsible for Animal Industry, Uganda Veterinary Board, Uganda Veterinary Association and the wider public.

Question7. What are the consequences of not observing drug withdrawal periods to human health?

Food and products of animal origin that are meant for human consumption shall contain drug residues that will pause a risk to human health. It is important to always observe drug withdrawal periods as indicated on the product labels. This calls for concerted efforts from all stakeholders concerned.