Farm constraints, cattle disease perception and tick management practices in pastoral Maasai community-Ngorongoro, Tanzania

E S Swai, A N Mbise, V Kessy, E Kaaya, P Sanka and P M Loomu*

Veterinary Investigation Centre, PO Box 1068, Arusha, Tanzania
emasw@yahoo.co.uk
* District Veterinary Office, PO Box 1, Loliondo, Tanzania

Abstract

A cross-sectional study was conducted in Ngorongoro areas of Tanzania to evaluate farmer perception of farm constraints, diseases and to investigate tick management practices during the period of March 2004. Major farm constraints were listed as diseases, lack of veterinary personnel, limited market and drug supplies and inadequate pastures. Of the diseases, tick borne diseases (TBDs) i.e. East Coast fever (ECF) was ranked first, followed by Anaplasmosis and Cowdriosis.

Most farmers reported applying acaricide at interval of 2 to 4 weeks; most used acaricides that require on farm dilution and most farmers incorrectly diluted the acaricide. Tick infestation rate was estimated to be 85.6% and overall mean tick density was 20.7 ± 2.2 tick/cattle. Rhipicephalus appendiculutus and Rhipicephalusevertsi evertsi ticks were those mostly frequently encountered on the cattle and degree of tick infestation varied significantly  between sub counties. Mature animals had higher odds of carrying ticks (of either spp) ([Odd ratio] ORs =12.3, P = 0.018) than young stock. None of the other farm- and animal-level factors investigated were associated with tick counts.

The study established gross misuse of acaricides, which has complicated effective tick control. Extension work by veterinary personnel and acaricide manufacturers needs emphasis to save our cattle and environment.

Key words: Acaricides, Africa, disease perception, farm constraints, pastoral livestock production system, Tanzania, ticks

Introduction

Tanzania has a huge livestock resource due to the agro-ecological zones that make the country suitable for livestock production. The country has approximately 50% of the cattle, 29% of the sheep, 40% of the goats and 24% of the chicken population of East Africa (FAO 2003). The livestock sub-sector contributes 30% of the national Agriculture Gross Domestic Product (GDP) and about 18% of the total GDP (Melewas and Rwezaula 1999). These livestock resources are only utilising 53% of the land that is suitable for grazing. The rest, 21% remain unutilised and 26% is tsetse infested (Anonymous 1996).

Ngorongoro district, predominantly a rangeland, covers an area of 15,341 km² and pastoralists keep approximately 300,000 cattle, 250,000 goats, 200,000 sheep and 16,000 donkeys (Anonymous 1994)

Ticks-obligatory ecto-parasites (vector of important livestock diseases like acomplexan tick borne diseases (TBDs) - Theileriosis, Babesiosis and Cowdriosis) are ranked second to mosquitos as the vector of most economical importance to livestock in Tanzania (Kagaruki 1991). Distribution of ticks is mitigated by the distribution of the appropriate host species and the 8 genera, 60 species and 2 unnamed species that are thought to exist in Tanzania (Yeoman and Walker 1967). Knowledge of tick numbers on cattle provides useful information on tick population dynamics, dynamics of disease transmission and estimates of resistance of different hosts (Norval et al 1992). Tick abundance is known to vary with time (season to season and year to year) and space (between habitats and ecological zones) due to interaction of numerous factors, such as host diversity and climate (Lightfoot and Norval 1982), the levels of resistance of hosts, absence of control measures and management practices that affect the host behaviour (Punyua and Hassan 1992). Generally, the seasonal activities of ticks are known to vary from species to species and country to country (Soulsby 1986) due to variation in photoperiod (Rachev 1987; Berkvens et al 1995), which necessitates their study in various countries and different agro-ecological zones.

Structured studies aiming at identifying tick species, tick control strategies and characterisation of factors influencing vector tick counts, and distribution amongst pastoralist cattle population in Ngorongoro (wildlife/livestock ecosystem) are limited and remain at large unconducted to date.

In the present cross-sectional study we aimed to further investigate the role of pastoralist cattle as hosts for ticks and identifying the major tick species, quantify them and explore tick control regimes currently in use at farm level.

Materials and Methods

Study area

Ngorongoro district lies between Latitude 2 to 4S and Longitude 35 and 36E. Four broad eco-climatic zones can be described namely: the cool humid highlands of Ngorongoro and Loliondo; the warm sub-humid plateaus; the semiarid zone within and adjacent to the Rift valley and the hot dry short grass plains. The altitude within these zones varies from 2000-3000 m above sea level in the highlands to 1000 m on the Rift valley floor at Lake Eyasi and Natron. Two distinct seasons are distinguished: dry season (June to November) and rainy season (December to May). Rainfall precipitation and distribution is highly variable and ranges from 1000 mm per annum in the highlands, to 800 mm on the high plateau and to below 600 mm on the dry short grass plains.

Livestock production system

Two systems of livestock production in Ngorongoro are distinguished. The pastoralism and agro-pastoralism that account for over 80% and less than 20% of the total area, respectively. Maasai and Tartog (85%-pastoralist) and Batemi (15%-Agro-pastoralist) are the major ethnic groups and their livelihood virtually depends on livestock. Livestock production in these systems is characterised by seasonal movements of livestock to exploit temporal and spatial availability of range resources as well as minimize disease risk. Two types of movements are distinguished: the vertical and horizontal. Vertical movements are movements between the lowlands and highlands while horizontal movements involve the same eco-climatic zone.

Study design

Four divisions, comprising 5 ward/ villages (sub-counties), namely Sale, Malambo, Pinyiny, Olpiro and Digodigo, 17 farms and 90 cattle of all sexes were randomly selected for the study. Selected cattle were categorised or 'classified by Maasai' into the following age groups: 1.5 to 3yrs ('young stock'): 56; >3 to 6 yrs ('immature'): 20 and > 6yrs('adult'): 14. Distribution of study animals by ward (sub-counties) is detailed in Table 1.

Data collection

Questionnaires that were extensively piloted prior to the start of the survey, administered on a single day farm visit, were used to collect all information related to animals (age, sex, source of animal-homebred or brought-in and owner) and farm management practices. Due to the absence of written records, age of animal was estimated by dentition. Data collected by the questionnaire (which comprised close ended questions - to ease precision of responses and analysis), included details on the farm constraints, major cattle diseases, type of acaricide (the trade name for the product), method of 'application' (by hand - spray, brush, in a dip-tank or spray race, by pour-on preparation or hand removal of ticks) and the interval between two acaricide treatments preceding the farm visit.

On each farm visit, the type of acaricide used most recently was recorded and the farmer was asked to demonstrate how the acaricides were diluted (if at all) for use on the cattle. The amount of water used for dilution was measured using a measuring cylinder, and the amount of acaricide that was diluted by this volume of water was measured using a 10 ml syringe. The actual dilution used was compared with the dilution recommended by the manufacturer. During the survey period, ticks (immature and adults) on all study animals were identified by genera and counted using standard procedures (Hoogstraal 1956). Body live weight (in kg) in relation to chest measure (in cm) of each individual animal was estimated using a tape weigh band (Webo-Denmark). Most of the responses to many of the questions were used as binary explanatory variables in the analyses described in the following section. The study was conducted during the period of March 2004.

Statistical analysis

Data were edited and performed in Epi-Info version 6.04d (CDC, Atlanta, USA). The presence of a tick of any species was investigated as a binary response (i.e. the animal had one or more ticks or none) in a logistic regression model using Egret for Window (Egret for Windows version 2.0, Seattle, USA). In these models, farm ID was incorporated as random effects to account for clustering of animals by farm (Diggle et al 1994). Graphical results were generated in the Excel Microsoft® software programme.

Results

Farm constraints and cattle disease perception

All selected farms were visited and interviews conducted (a 100% response rate). The average herd size was 38 (range 5 to 130). Major farm constraints that were ranked in the order of importance included cattle diseases (94%, 16/17), lack of vet personnel, (6/17, 35.2%), lack of livestock market (28.6 %) and lack of feeds during the dry season period (25.2%). Of the cattle diseases, TBDs were singled out and ranked as the most important diseases. Of the TBDs, East Coast fever (ECF), Anaplasmosis and Cowdriosis were ranked as the most killer diseases.

Tick infestation

Five tick species were identified during the survey with Rhipicepahalus appendiculutus being the most abundant accounting for 67.5%, followed by Rhipicephalus evertsi evertsi, 13.9%, Amblyomma variegatum 10.8%, Hyalomma spp 6.1% and Boophilus decolaratus 1.4 % in the order of abundance (Table 2).

Of the 90 cattle examined, 77 were found to carry ticks, giving an infestation rate of 85.6% and the overall mean (mean ± SE) tick density of 20.7 ± 2.2 ticks/animal. The mean tick specific densities per ward are detailed in Table 1. Tick infestation rate was significantly (χ2 =15.5, df = 4, P = 0.003) higher in Digodigo, Sale and least in Malambo. 45% of the tick infested animals carry more than 25 to 50 different tick species (Figure 1). The mean tick specific density per animal was estimated to be 13.9 ± 1.9 for Rhipicephalus appendiculutus, 2.76 ± 0.6 for Rhipicephalus evertsi evertsi, 2.5 ± 0.5 for Amblyomma variegatum , 1.2 ± 0.3 for Hyalomma spp and 0.3 ± 0.1 for Boophilus decolaratus.

Tick management practices

Most interviewed farms (82.4 %, 14/17) claimed to practice some form of tick control. Over 50% used acaricide for tick control either once or twice per month and there was no variation (P>0.001) between wet and dry seasons (Figure 2).

Chlorfenvinphos-based acaricide (Stelladoneâ, Norvatis-Kenya) was that used by most farmers with amitraz (12.5% w/v) compounds such as (Tixfixâ Twiga Chemical Industries, Dar-es-Salaam, Tanzania) being the second most often used acaricide. No synthetic pyrethroid containing preparations were reported to be used. Acaricide application was mostly carried out by the farm owner (76.1%) and to a lesser extent by relative or son (16.7%). Hand spraying was the most common method used (82.4%).

There were striking differences in the concentrations used on different farms. 35% farms, which used Stelladone, and 35% farms, which used Tixfix, were using over-strength concentrations. On the other hand, 65% farms, which used Stelladone, and 65% farms, which used Tixfix, used these acaricides at concentrations less than those recommended by the manufacturers. No farms used the correct concentration (Figure 3, Figure 4).

The results of the final multivariable analyses are summarised in Table 3. The animal level variable found to be associated with tick infestation was age and weight of the animal. These variables were highly confounding, but age provides the best model fit. Older animals were more likely to have adult ticks (of any species) than young animals. None of the other farm- and animal-level variables investigated were found to be associated with tick infestation in either univariate or multivariate model.

Discussion

The importance of ticks and TBDs as number one killer diseases cannot be overemphasized. The high rate of awareness as reflected by high tick control response rate is the clear evidence of this fact. However, the data in Figures 3 and 4 reveal a great deficiency in the use of the two acaricides in the surveyed farms. Most farms over diluted the acaricide and used them at levels below the manufacture's recommendation. These malpractices are possibly due to a number of factors. Lack of veterinary personnel and shops to advise on purchase of inputs including acaricide and spray pumps, as reflected from the findings of this study, could be one amongst several reasons. Under such a situation, farmers are likely to continue to use low concentrations as a way of economising on the use of the product, so that it lasts and serves longer. Other possible explanations for incorrect dilution of acaricide includes lack of appropriate measures for both acaricide and a diluent, lack of knowledge on application and correct dosing of acaricide. It was also observed that some acaricide containers had instructions written in 'English' (or were missing altogether) instead of 'Swahili' - the local official language (vernacular). This may well have contributed to inappropriate dilution of the acaricide.

Improper use of acaricide (under dosing) can expose ticks to sub-lethal strengths of acaricide leading to the possible danger of mounting resistance (Wellcome East Africa 1980; Kagaruki 1991). Over dosing is a waste of money and detrimental to the environment and possibly to the farmers health too.

During this study, Rhipicephalusappediculatus ticks were consistently the most abundant of the five commonest tick species. This may be because cattle are widely believed to be the primary host for this tick to which their resistance has been reported to be lower under field condition (Lightfoot and Norval 1982; Kaiser et al 1982). The other tick species (Rhipicephalus evertsi evertsi, Amblyomma variegatum , Hyalomma spp and Boophilus decolaratus) occurred in very low numbers, suggesting that they are less abundant under field conditions. The low number of tick species on young stock (24%) compared with cows suggest that young stock are less attractive to ticks than cows because they are protected by some form of innate age-related resistance (Wickel and Bergman 1997; Sutherst at al 1982). Since host-seeking activities of these ticks involves awaiting hosts at vantage position on vegetation, they have greater chance of attaching to cows than young stock because of the greater body surface. It is possible that these differences may be attributed to continuous selective grooming of the calves heads, ears, and neck from their respective dams (Fivaz and de Waal 1993) or grazing management practices since calves less than 3 months of age are rarely released to graze with their dams.

Conclusions

• The study identified the most important farm constraints (diseases), the most important tick species(Rhipicephalus appendiculutus) and established gross misuse of acaricides in the control of cattle ticks.

• There is a need to conduct more extensive and detailed studies covering larger areas of pastoralist land.

• The current tick control practice will in the end not to be economical if misuse of acaricide continues. The solution may lie in adoption of integrated tick control measures that will involve intensive education of farmers on tick population dynamics and proper use of acaricides.

•  Manufactures of acaricides need also to provide "easy to follow"instructions and well-calibrated measurement containers for use by farmers and stockmen.

Acknowledgements

The authors wish to acknowledge the financial support from DANIDA-ERETO without which this research would not have been possible. Special thanks go to the participating farmers for their cooperation and help. Permission to publish this paper was granted by the Director of Veterinary Service, Tanzania for which we are very grateful.

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