ABSTRACT
Tick infestation of cattle remains one of the major constraints to cattle production in Africa. Reduction of ticks should, therefore, enhance cattle production which is critically needed to ensure economic and food security. In the current study, 59 farmers were interviewed about the types of pesticides available for routine pest control on their farms. There were different types of acaricides commercially available for use in Ghana and the addition of new types from different companies is growing rapidly. The results also revealed the three leading types of acaricides; Milbitraz, Eraditick, and Amiraz, which were popular among farmers. There was overwhelming evidence of the uncontrolled use of different acaricides against ticks. Tick species were most likely exposed to the commonly used active ingredients in acaricides namely, amitraz, representing the amidine group and pour-ons from the cypermethrin group. The results also showed that Eraditick was the most preferred among amitraz-based formulations, representing the predominant acaricides on all cattle farms. Overall, farmers in Ghana used different methods of tick control. However, strategic acaricide application, via spraying with the knapsack sprayer was the preferred method for resource-poor farmers.
The strengths (toxicity) of the most commonly used active ingredients of products were tested in a dose-dependent fashion against ticks feeding on cattle by comparing 1) the number of dead ticks and 2) time of re-infestation. Generally, the killing activity of the prototypical non-systemic emulsifiable concentrate was thrice faster than the cypermethrin group referred to as the “pour-ons.” Specifically, spraying with Eraditick resulted in clearance of >50% of the population of targeted ticks within 24 hours as compared with 72 hours required by either Cypertop or Zerotick. There was no difference in the toxicity between the use of higher concentrations and the recommended dose of the manufacturer (p=0.814) because increasing
the dosage of acaricides did not result in a corresponding increase in the number of dead ticks.
Notably, 70% of farmers used 1-3 types of acaricides, in rotation or simultaneously. However, complete tick clearance was not achievable even with a combination of two or more amitraz-based formulations. From the current study, the re-infestation rate of tick species ranged from 10 ticks/day to 30 ticks/day. Regardless of the number of types and dosage of different non-systemic acaricides tested, the re-infestation time of ticks to cattle occurred within 7 days, post-application.
On the contrary, the results have demonstrated the possibility of combining the acaricidal effects of the emulsifiable concentrate-based acaricide (Eraditick) with pour-on based (Cypertop) to improve toxicity in tick populations. This combination was able to kill >80% of tick species as compared to 50-60% using the traditional acaricides alone. It equally achieved a near-zero clearance of ticks within 6 days of application that was impossible with the other alternative pairings. Notably, this chemical association consistently cleared all ticks from different groups of animals and delayed re-infestation with new ticks for over 14 days. The huge difference in the acaricidal strength has a significant effect on both the time it takes to clear the existing ticks and the re-infestation rates of new ticks to the previously treated cattle. Altogether, results from the current study are big findings that could transform the way we control livestock ticks. This could reduce the cost of producing animals and improve livelihoods by reducing poverty among cattle farmers.
CHAPTER ONE
INTRODUCTION
In Ghana, livestock provides cash income required to reduce poverty among the majority of cattle farmers. For example, in many impoverished communities in Ghana, the ownership of cattle ensures food and economic security. Generally, animal production plays a central role in the livelihood of smallholder farmers in Africa (Kaasschieter et al., 1992; Steinfield, 2003; Delgado, 2005; Thornton, 2010). Improving the health of livestock in resource-poor areas of the world will, therefore, not only provide economic and food security but also, improve human health and wellbeing.
The potential for cattle production on a commercial scale is enormous in the endemic tropical region (Thornton et al., 2007). This is evident in the availability of vast feed resource, providing the rationale for countries in the region to achieve a net meat production. Unfortunately, the prospect of attaining this goal is constrained by the risk of tick infestation. In Sub-Saharan Africa, ticks and associated tick-borne diseases account for the majority of disease-related mortality of cattle (Bell-Sakyi et al., 2004). Since disease remains a major threat to cattle production in the tropics (Molefi et al., 2017), the reduction of the threat of ticks, for example, should enhance the performance of the beef and dairy industry.
The challenge of ticks and tick-borne diseases remain even more likely in the tropics due to the favourable humid conditions offered by the tropical climate that allows ticks to complete their lifecycle and reproduce abundantly (Pal et al., 2001). Tick species, by the nature of their feeding habits, ingest a wide diversity of pathogenic organisms that cause diseases in cattle.
The most effective approach to limiting their competence is by direct killing using physical or chemical means.
Acaricides are the commonly used chemicals for the control of vector ticks that transmit infectious diseases to livestock (Stafford, 2007; Walker, 2014). During the last quarter of this century alone, more than 50 different types of acaricides were produced for livestock farmers (Extentresearch.com, 2018). With the widespread availability and ease of access, one may think that control of vector-borne-related diseases of livestock would be easier than ever, but this seems not to be the case. Rather, there is the emergence of new strains of ticks that are more aggressive and competent with increased resistance to chemical applications (Ninsin and Koney, 2016). Several factors, including the mode of application, may be responsible for the current spate of increasing tick resistance to generic brands of acaricide formulation (Koney and Nipah, 2000). However, batch-to-batch production and application of less effective formulations most likely increase the likelihood of tick adaptation to these chemicals resulting in the spread of resistant vector strains (George et al., 2004).
The adverse effects ticks impose on animal production provide the rationale to search for applicable tick control measures that would be effective. The current study examined the effectiveness of three of the leading types of chemicals. These acaricides represent the most commonly sold on the market and used regularly by farmers to control tick species on cattle farms in Ghana. The goal of this study was to identify the most potent combination of an acaricide treatment regime that could revolutionize tick control among farm animals. It was predicted that the cost of production could be significantly reduced if farmers would spend less time and money on pest control. Currently, it is possible to combine Amiraz and Eraditick to increase efficacy over the commercial formulations of amitraz-based acaricides or cypermethrin groups commonly referred to as “pour-ons”. This result was verified in
cattle herds at Amrahia Dairy Farm and in the study herd of Friesian x Sanga kept by the University of Ghana (Futse et al., unpublished). However, not all the acaricide combinations were toxic to the ticks. Many of the acaricide-mixes, when applied to cattle, have failed to kill the ticks. For the few that have completely cleared ticks from cattle, the time to re- infestation with new cohorts of ticks occurred within days (Futse et al., unpublished). Notably, some of the chemical associations consistently cleared all ticks from the groups of animals and prevented re-infestation with new ticks for over 7 days (Futse et al., unpublished). The differences in the time (<48 hours) it takes to clear the existing infestation and to prevent the return of new cohorts of ticks to the previously treated cattle are important findings that could transform the way livestock farmers use acaricides which could lead to a reduction in the cost of production in livestock farming.
Justification
Cattle production remains the main source of income for farmers but it is constrained by tick infestation (Sonenshine et al., 2006). Ticks and their associated diseases continue to impose costs on cattle production. The ability of ticks to transmit a wide range of microorganisms makes them very important. Diseases transmitted by ticks are the main health and management constraint faced by the ruminant industry. In the absence of effective control, livestock farmers can incur losses above $13.9 to $18.7 billion per year due to the mortality of animals (De Castro, 1997). A study by Kivaria (2006) estimated losses caused by tick- borne diseases to reach $364 million.
Generally, the problem of ectoparasite infestation (such as tick infestation) is a major hindrance to stock-raising in countries of the tropics. Putting the case of Rhipicephalus microplus into perspective, the full biologic cycle is confined to the mammalian host. Under conditions of heavy infestation, feeding activities of the adult instars will cause physical damage to the udder, hide and limbs. Specifically, cattle that were affected are most unlikely to be productive. The result will be a substantial drop in meat and milk production followed by extreme poverty among farmers (Ibelli et al., 2012). Not only could ticks damage the host and cause a decline in productivity, but they also transmit different types of animal diseases that may be directly transferable to the farmer and consumers of livestock products.
Tick-borne diseases are not possible without ticks. It takes a bite of a feeding tick to transmit disease to a susceptible host. Subsequent inter-host transmission of infection will increase if farmers failed to control tick infestation of the herd. For this reason, research is urgently required to identify efficient approaches to controlling ticks in a way that will lessen the burden on the resource-poor farmer. Acaricides are by far the most effective means of treating tick-infested cattle. However, the high cost of using acaricide can become a key limitation to its use. In most cases, desperate farmers resorted to buying less effective
pesticides or using sub-optimal doses. The practice of implementing low-dose chemical formulation against ticks and other pests of livestock can accelerate the process of these organisms becoming resistant to pesticides. The availability of data on the dose and schedule of application of commonly used acaricide will provide the literal lifesaver resource-poor livestock farmers will need in the real-life setting. Animal husbandry cannot be sustained without the use of acaricides (Kröber and Guerin, 2007). In Ghana, cattle and other ruminants are being exposed to a wide variety of pesticides. It is common knowledge that heavy ectoparasite infestation signals the death of animals. Animals that were free from ticks produce more milk and meat than those infested with ticks (Sajid et al., 2007). Farmers believed that indigenous cattle are naturally tolerant of tick infestation. Conversely, the highly productive exotic breeds and the crosses between those breeds and the indigenous cohorts are highly sensitive to ticks. Absence of an applicable pest control program, based on frugal use of acaricide, therefore means an outright loss of the opportunity to upgrade indigenous cattle by way of cross-breeding. Also, the return rate of ticks after acaricide use is high and the return period short. With such a short return period to re-infestation with new cohorts of ticks, the majority of farmers resorted to using them frequently or trying different types of acaricides to save their herd from damage and tick-transmitted diseases. This practice has led to the overuse of acaricides and the development of resistant vector species. In short, the emergence and spread of such pests including the tick and tsetse fly would make it impossible to control future generations of pests of livestock. Understanding the key determinants of re-infestation is therefore central to finding the optimal dose and type of pesticides the farmer will need to improve production. Results from the current study will guide the implementation of acaricide schedules in doses that will prolong re-infestation time, thus reducing the need to use acaricides too frequently. This approach will not only optimize cattle production but also reduce the cost of production. The benefit of getting the precise
application regime will not only minimize excessive exposure of stockmen to chemicals but also reduce the high possibility of overuse. From the standpoint of global health, raising the awareness of the availability of effective acaricide will accelerate the process of farmers producing pesticide-free meat and milk that consumers will readily accept. It will also ensure the improved health of consumers and reduce the cost of healthcare.
Hypothesis
Under natural conditions of tick infestation on pasture, the time to re-infestation of ticks on cattle is dependent on the dose and type of acaricide used.
Objectives
- Identify the acaricide (from the various ones on the market) that effectively kills ticks within the shortest time.
- Determine whether the re-infestation of cattle previously treated with a specific acaricide is dependent on the dosage applied.
