The impact of 2 dipping systems on endemic stability to bovine babesiosis and anaplasmosis in cattle in 4 communally grazed areas in Limpopo Province, South Africa

A 12-month study was conducted in 4 communal grazing areas in the Bushbuckridge region, Limpopo Province, South Africa. The main objective was to investigate the impact of reduced acaricide application on endemic stability to bovine babesiosis (Babesia bigemina and Babesia bovis) and anaplasmosis (Anaplasma marginale) in the local cattle population. To this end 60 cattle in each communal grazing area were bled at the beginning and the conclusion of the experimental period and their sera were assayed for B. bovis, B. bigemina and Anaplasma antibodies. Cattle in the intensively dipped group were dipped 26 times and maintained on a 14-day dipping interval throughout the study, whereas cattle in the strategically dipped group were dipped only 13 times. Three cattle, from which adult ticks were collected, were selected from each village, while immature ticks were collected by drag-sampling the surrounding vegetation. During the dipping process, a questionnaire aimed at assessing the prevalence of clinical cases of tick-borne disease, abscesses and mortalities was completed by an Animal Health Technician at each diptank. An increase in seroprevalence to B. bovis and B. bigemina and a decrease in seroprevalence to Anaplasma was detected in the strategically dipped group while in the intensively dipped group the converse was true. Amblyomma hebraeum was the most numerous tick species on the cattle, and Rhipicephalus (Boophilus) microplus was more plentiful than Rhipicephalus (Boophilus) decoloratus. Drag samples yielded more immature stages of A. hebraeum than of Rhipicephalus (Boophilus) spp. The incidence of clinical cases of tick-borne disease and of abscesses increased in the strategically dipped group at the start of the survey.     

An epidemic of East Coast fever on a dairy farm in eastern Tanzania

During the period August-September 1995, an epidemic of East Coast fever occurred at a dairy farm in Morogoro region of eastern Tanzania. Due to an intensive dipping scheme since 1970, a very unstable endemic status had been established in the animals. A breakdown in the dipping scheme caused a major disease outbreak; the dip wash was not changed for 18 months prior to the outbreak and dipping continued in a dip wash of unknown strength. There was also a delay in detecting the disease at an early stage. In total, 180 out of 432 (42%) of the cattle at the farm died--resulting in a loss of Tshs. 26,330,000 (US$ 42,879). The attack risk was nearly 77%. The outbreak points to the importance of adopting integrated strategies for the control of ticks and tick-borne diseases.     

Causes of mortality in impala (Aepyceros melampus) on 20 game farms in Zimbabwe

The most common cause of death in impala (Aepyceros melampus) herds on 20 game farms in Zimbabwe was stress or physical injury during capture. Acute fascioliasis due to Fasciola gigantica was identified as the main disease problem associated with smaller game farms and where impala had been recently introduced. Losses associated with ticks and tick-borne diseases were rare. Impala in Zimbabwe are maintained in a healthy condition on game farms where they are given supplementary feed during the dry winter.     

Financial analysis of dipping strategies for indigenous cattle under ranch conditions in Uganda

A financial analysis was performed to assess the performance of three acaricide-treatment groups of indigenous breeds (Zebu and Nganda) of cattle on a ranch in Luwero District, Uganda. The treatments were based on different frequencies: twice-a-week dipping, once-a-month dipping and no tick control. The objective was to evaluate the economic justification for intensive acaricide application for tick and tick-borne disease control in Uganda. Data were collected by monitoring cattle performance over a period of 34 months. Biological data collected included the number of cows at the beginning and end of the study, net starting liveweight, number of calves born, number of animals dying due to tick-borne diseases and other causes, number of animals sold or slaughtered and milk yield. Records of variable costs (acaricides, drugs, labour, etc.) and output prices were assembled and calculated by treatment group. Gross margin and marginal analysis were used in the financial analysis. The exchange rate in 1990–1993 was one US$ to 1200 Uganda shillings. The gross benefits obtained from animal sales, herd value and milk yield were Uganda shillings 1175, 1389 and 1311 per kg of net starting liveweight for animals dipped twice-a-week, once-a-month and not dipped, respectively. The variable costs were Ug. shs. 424, 390 and 360 per kg of net starting liveweight, respectively. Consequently, the gross margins were Ug. shs. 751, 999 and 951 per kg of net starting liveweight. Furthermore, the marginal rate of return (MRR) in changing from no tick control to once-a-month dipping was 160%, while changing from no tick control to twice-a-week dipping was negative (− 313%). The above results showed that the value of increased gains in production obtained from twice-a-week dipping strategy does not offset the costs of inputs for intensive dipping. Once-a-month dipping (strategic) therefore appears to be the most-profitable tick-control strategy for the farmer. The need to conduct further studies in different livestock- production systems and to rationalise future tick control policies is discussed.     

Communal cattle farmer’s knowledge,attitudes and practices on ticks (Acari: Ixodidae), tick control and acaricide resistance

The aim of this study was to reveal communal farmer’s knowledge, attitudes and practice on ticks and tick-borne diseases affecting cattle, tick control methods used and their knowledge on acaricide resistance. A total of 160 structured questionnaires are prepared and randomly administered to cattle farmers in Sinqu and Elundini communities in the Eastern Cape Province, South Africa. Associations between the area, gender, age, employment, source of income, level of education and farming experience were statistically tested using Chi-square test. Gall sickness (63%) was the most prevailing tick-borne disease in cattle during the summer season (61%). About 59% of the farmers had no knowledge of the effect of tick-borne diseases on cattle production, and 78% of respondents reported that ticks are the major challenge to cattle farming. Pour-on (61%) was the most commonly used acaricidal treatment system with every fortnight (40%) treatment frequency during the summer season and (31%) during the winter season. Pyrethroids (73%) were the most used acaricide compounds to control ticks, and about 65% of respondents perceived to have no knowledge of the use of ethnoveterinary medicines used to control ticks. Inefficacy of acaricide (44%) and undipped animals (42%) were regarded as the major contributing factors to the increased tick population and acaricide resistance. About 85% of respondents perceived that they do not practice acaricide rotation and 88% of the respondents had no knowledge of the acaricide resistance. Within the context of this study, ticks and tick-associated diseases are perceived by these farmers as the most important disease problem their cattle face. Thus, knowledge regarding the epidemiology of ticks and tick-borne diseases is key to control strategies, and farmer training should be encouraged to achieve better control of ticks and the diseases they transmit.

     

Strategies,Effectiveness and Rationale of Vector-borne Disease Control in the Pastoralist System of South-western Uganda

In Uganda, control of vector-borne diseases is mainly in form of vector control, and chemotherapy. There have been reports that acaricides are being misused in the pastoralist systems in Uganda. This is because of the belief by scientists that intensive application of acaricide is uneconomical and unsustainable particularly in the indigenous cattle. The objective of this study was to investigate the strategies, rationale and effectiveness of vector-borne disease control by pastoralists. To systematically carry out these investigations, a combination of qualitative and quantitative research methods was used, in both the collection and the analysis of data. Cattle keepers were found to control tick-borne diseases (TBDs) mainly through spraying, in contrast with the control of trypanosomosis for which the main method of control was by chemotherapy. The majority of herders applied acaricides weekly and used an acaricide of lower strength than recommended by the manufacturers. They used very little acaricide wash, and spraying was preferred to dipping. Furthermore, pastoralists either treated sick animals themselves or did nothing at all, rather than using veterinary personnel. Oxytetracycline (OTC) was the drug commonly used in the treatment of TBDs. Nevertheless, although pastoralists may not have been following recommended practices in their control of ticks and tick-borne diseases, they were neither wasteful nor uneconomical and their methods appeared to be effective. Trypanosomosis was not a problem either in Sembabule or Mbarara district. Those who used trypanocides were found to use more drugs than were necessary.     

The Impact of Tick Control on the Productivity of Indigenous Cattle under Ranch Conditions in Uganda

The impact of tick control on the productivity of indigenous cattle was investigated in three herds of East African shorthorn Zebu and Zebu×Ankole (Nganda) breeds, maintained under three tick management systems practised under ranch conditions: twice-a-week dipping, once-a-month dipping, and no tick control. The milk production and the growth rates of pre-weaned and post-weaned calves were monitored once a month over a period of 34 months. Milk offtake was 23% higher during the heavy rainy seasons than in the long dry seasons. Twice-a-week dipping increased the milk offtake by 21% in the second year of study and prolonged the duration of lactation in cows. Similarly, twice-a-week dipping increased the pre-weaning growth rate by 39% in the second year of study, but had no significant effect on the post-weaning growth rate. Generally, the growth rate of calves were greatest during the heavy rainy seasons and least during the long dry seasons. These results provide a basis for assessing the losses under different tick management systems in the various production systems.     

Some aspects of tick-borne diseases of British sheep

The significance of tick-borne fever (TBF) and other tick-borne diseases of British sheep are reviewed. Experimental and field studies were carried out to clarify the role of TBF as a pathogen per se and as a predisposing factor in other diseases. Experimental TBF infection caused anorexia and depression in two- to three-week-old lambs, which under the stress of a hill environment could alone be a cause of mortality. Nine out of 10 lambs experimentally inoculated with Staphylococcus aureus during the febrile phase of a TBF reaction developed pyaemic lesions compared with four out of 20 lambs inoculated with S aureus alone. Specific pathogen-free lambs inoculated with an aerosol of Pasteurella haemolytica serotype A1 during a TBF reaction showed more severe clinical signs and had more extensive pathological changes at necropsy than control lambs given P haemolytica alone. Dual infection with TBF and louping-ill virus showed that not only were dually infected sheep more susceptible to louping-ill but almost all of them succumbed to a haemorrhagic syndrome involving a systemic mycotic infection with Rhizomucor pucillus. None of eight sheep given louping-ill virus alone developed this syndrome. Field studies indicated that morbidity and mortality in lambs in south-west Scotland could be markedly reduced by dipping and long acting antibiotic prophylaxis. Lamb groups in which both of these were carried out incurred losses of only 0.6 per cent compared with 10.3 per cent in control groups. In addition antibiotic-treated lamb groups demonstrated significantly better weight gains than untreated groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Controlling tick infestations and diseases in sheep by pour-on formulations of synthetic pyrethroids. A field study

The use of synthetic pyrethroids in pour-on formulations reduced tick infestations and the incidence of tick-associated diseases in lambs more than dipping in organophosphate acaricides. Though the use of pyrethroids did not prevent the lambs from being infected with tick-borne fever (TBF), the incidence of lambs with lameness (tick pyaemia) or lambs suddenly found dead (Pasteurella haemolytica septicaemia), which often are seen in association with TBF, was reduced. The use of pyrethroids for three years did not seem to affect the prevalence of TBF.     

The control of heartwater on large-scale commercial and smallholder farms in Zimbabwe.

As part of a series of studies associated with the development of improved vaccines for heartwater (a tick-borne disease of ruminant livestock caused by Cowdria ruminantium), field surveys were carried out to assess losses associated with the disease and the costs associated with controlling it in the two main agro-ecological zones of Zimbabwe (lowveld and highveld) where heartwater is believed to be endemic and epidemic, respectively. In each zone, a cross-sectional study was performed in the main farming systems (smallholder (SH) and large-scale commercial (LSC) beef and dairy), followed by longitudinal studies in the same sectors to improve data accuracy for some parameters. Suspected heartwater-specific mortality in cattle was similar in all LSC sectors (p = 0.72) accounting for a median 1% mortality risk. Heartwater-specific mortality in SH areas was not assessed due to poor diagnostic ability of the farmers. Few LSC farms and SH households kept sheep; suspected heartwater-specific mortality in LSC sheep was 0.8% in the lowveld and 2.4% in the highveld. Goats were a major enterprise in SH areas but not on LSC farms. Suspected heartwater mortality in LSC goats was 0.8% at one site in the highveld and 17.5% on a farm in the lowveld. Application of acaricides was the major control method for heartwater and other tick-borne diseases on both SH and LSC farms. On LSC farms, plunge dipping was used most frequently and the number of acaricide applications ranged widely between 3 and 52 per year. The total cost of acaricides per head per annum was higher in highveld dairies than in highveld and lowveld beef enterprises (p = 0.03). In SH areas, cattle plunge dipping was conducted by the government with an average frequency of 8 +/- 2 (sd) immersions per annum in both the lowveld and highveld. The type of tick control on sheep and goats in all production systems was highly variable (ranging from none to hand removal or intensive acaricide treatment). Suspected heartwater cases on LSC farms were treated with tetracyclines; treatment was not reported in SH areas. Reported treatment costs were high (median Z$ 120) and highly variable (range Z$-833). Vaccination against heartwater with the live, blood-based vaccine was reported on only one LSC farm. LSC farms applying acaricide 30 or more times per year reported higher morbidity (p < 0.0001) and mortality (p < 0.0001) than farms applying acaricides less than 30 times a year. This finding supports the use of reduced tick control in the management of heartwater in Zimbabwe.     

Ixodid ticks on cattle belonging to small-scale farmers at 4 communal grazing areas in South Africa

Ixodid ticks were collected during the period September 1991 to August 1993 from cattle belonging to small-scale farmers utilising 4 communal grazing areas. Three of these were in North West Province and 1 in Mpumalanga province, South Africa. Ten tick species were collected in North West Province and 7 in Mpumalanga. The adults of Amblyomma hebraeum, Rhipicephalus appendiculatus and Rhipicephalus evertsi evertsi were most numerous in North West Province, while in Mpumalanga Boophilus decoloratus comprised more than 75% of the total population. Amblyomma hebraeum was present on all grazing areas, and heavy infestations of adults occurred during the period October to May on 1 of these. Few B. decoloratus were collected in North West Province, chiefly because the sampling method was inadequate, and most of these were present during early summer (October to December) and late summer and autumn (March to May). The initially low population of B. decoloratus in Mpumalanga increased substantially towards the conclusion of the survey, probably because of the cessation of dipping. Boophilus microplus was present in small numbers on 2 grazing areas in the North West Province. Adult Hyalomma marginatum rufipes reached peak numbers from December to February and Hyalomma truncatum from February to April in the North West Province. Only H. marginatum rufipes was collected in Mpumalanga. Rhipicephalus appendiculatus was present on all the grazing areas, with most adults present from December to April. Most adult Rhipicephalus evertsi evertsi were collected from September to April and Rhipicephalus simus was present during the period October-April.     

A longitudinal study of sero-conversion to tick-borne pathogens in smallholder dairy youngstock in Tanzania

A longitudinal study of sero-conversion of youngstock to the tick-borne pathogens Theileria parva, T. mutans, Anaplasma marginale, Babesia bigemina and B. bovis was conducted over two years on smallholder dairy farms in Tanga region, Tanzania. There was evidence of maternal antibodies to all tick-borne pathogens in animals less than 18 weeks of age. Seroprevalence increased as expected with age in animals older than this but seroprevalence profiles underestimated the force of infection due to waning antibody levels between samplings. By the end of the 2-year study, less than 50% of study animals had seroconverted to each of the tick-borne pathogens investigated, consistent with the low levels of tick attachment observed on the study animals. Some associations between seroconversion to tick-borne pathogens, and counts of their known tick vectors on the animals, were identified as expected. However, some were not, suggesting that counts of some tick species may act as an index of rates of attachment of other vector species. Variation in acaricide treatment frequencies was not associated with variations in tick-borne pathogen seroprevalence suggesting that acaricides may be used more frequently than necessary on many farms. Most animals were zero-grazed, a management system associated with a significantly lower likelihood that animals seroconverted to any tick-borne pathogen except A. marginale. Seroprevalence varied locally with farm location (particularly for Babesia spp.) but was not well predicted by indices of ecological conditions. Our findings suggest that attempts to achieve a state of 'endemic stability' for tick-borne pathogens may be unreasonable on the smallholder dairy farms studied but reductions in the frequency of use of acaricides may be possible following prospective studies of effects on mortality and morbidity due to tick-borne pathogens.     

Efficacy of long-acting oxytetracycline for the prevention of tick-borne fever in calves

Twenty-six calves which had not previously grazed tick-infested pasture were divided into two equal groups. On May 26, 1988 (day 0) they were turned out into a field of rough grazing where cases of redwater fever had occurred the previous spring. Seven, 14, 21 and 28 days after the start of the trial the animals in one group each received an intramuscular injection of 20 mg/kg bodyweight of long-acting oxytetracycline. During the 60 days of the trial the animals received a severe tick-borne fever challenge, in some cases combined with a redwater fever challenge. An unforeseen complicating factor was the presence of animals persistently infected with bovine viral diarrhoea virus, present in almost equal numbers in both groups. At the end of the trial the treated group weighed on average 16 kg more than the control group, a difference which was attributed to the suppression of tick-borne fever by oxytetracycline.     

The role of parasitic diseases as causes of mortality in cattle in a high potential area of central Kenya: a quantitative analysis

Postmortem records of cattle brought to the Veterinary School in Kabete near Nairobi were examined for a period of 15 years (1984-1998, inclusive) in order to establish the role that parasitic diseases played as causes of death. The cattle were mainly of exotic breeds but a few were crosses or of indigenous breeds. There was a total of 1413 cases of deaths from various diseases of which 177 (13%) were due to parasites. The tick-borne diseases were in high proportions and accounted for 84,7% among the parasitic causes, which represented 10,6% of all the deaths recorded. The main tick-borne disease was East Coast fever (ECF) (65%) followed by heartwater (10,2%), babesiosis (5,1%) and anaplasmosis (4,5%). Hydatidosis was responsible for 7,3% of deaths from parasitic causes. Deaths from ECF were recorded in all the 15 years and in high proportions compared to those due to heartwater (8/15), babesiosis (7/15) and anaplasmosis 5/15). Over the period under consideration, no decline was noted among various disease conditions despite advances made in controlling tick vectors and in the treatment of various parasitic conditions. The area covered by this study has the advantage of having several veterinary-related institutions close by. Hence knowledge and awareness about livestock diseases is relatively high compared to other parts of the country. It is therefore challenging to the Veterinary Department to examine the service delivery systems and other factors that may contribute to the persistent presence of these fatal parasitic conditions of cattle.     

Tick infestation of Borana cattle in the Borana Province of Ethiopia

A study was conducted to identify and determine burdens of ticks infesting Borana cattle in the Borana Province of Ethiopia. Rhipicephalus pulchellus, Rhipicephalus pravus, Rhipicephalus muhsamae, Rhipicephalus praetextatus, Rhipicephalus evertsi evertsi, Amblyomma gemma, Amblyomma variegatum, Amblyomma cohaerens, Amblyomma lepidum, Hyalomma truncatum, Hyalomma marginatum rufipes and Boophilus decoloratus were identified on the cattle. Their burdens ranged from 658-1,554 with a mean of 1,205 ticks per animal. Out of the total 6,025 ticks collected, about 82% were R. pulchellus, followed by R. pravus (about 8%) and A. gemma (5%). The other nine species of ticks accounted for only 5% of the total burdens. It is suggested that a strategic tick control method, aimed mainly at reducing the R. pulchellus burdens, with the objective of allowing a reasonable number of ticks to remain on cattle for the maintenance of endemic stability to tick-borne diseases be instituted.     

Socio-economic factors influencing control of vector-borne diseases in the pastoralist system of south western Uganda

Research in control of tick-borne diseases and trypanosomosis, and their vectors, namely, ticks and tsetse flies respectively, has been on going for decades. However, very little attention has been paid to the socio-economic factors that are likely to influence the outcome of the interventions in the control of these diseases. Thus, this study was designed to investigate these factors, mainly the intra-household factors influencing decision-making in the control of Vector-borne diseases in the pastoralist areas of Uganda. These factors included: indigenous technical knowledge, household economic factors, and gender. Both qualitative and quantitative methods were used in the collection and analysis of data. The tools used for data collection included among others, participatory learning and action (PLA), and Case studies. The findings included the following: In pastoralist households, a big proportion of the household budget was allocated to vector-borne diseases control. In the male-headed households, men dominated decision-making on vector-borne diseases control, although the goals and priorities of men and women in these households were not the same. Also, vector-borne disease control was predominantly by use of modern veterinary drugs, and pastoralists treated sick cattle by themselves even in situations where there were veterinary personnel.     

Market value and managerial decisions: implications from a decade of feeder cattle teleauctions.

Data from feeder cattle teleauction sales in Georgia from 1977 to 1988 were analyzed using least squares analysis of variance to detect significant (P less than .05) influential factors on price. The sample was divided into two periods, 1977 to 1982 and 1983 to 1988, to test whether the influence of factors had changed over the time periods. The test of equality was rejected (P less than .01) using a Chow test, thus suggesting a change had occurred. Hereford breeds were discounted in the latter period whereas Angus breeds generated a premium in the earlier period. Treatment for specific diseases resulted in premium prices, as did preconditioning, during the 1983 to 1988 period. The effect of seasonality on prices decreased over the two time periods. The optimal lot size increased from 228 to 280 cattle during the time periods.     

Effect of the interval between shearing and dipping on the spread of Corynebacterium pseudotuberculosis infection in sheep

OBJECTIVE: To determine whether the spread of Corynebacterium pseudotuberculosis infection to sheep in dips could be controlled by increasing the time between shearing and dipping. DESIGN: A controlled treatment trial where only the time between shearing and dipping was varied. ANIMALS AND PROCEDURE: One hundred and ninety-five sheep were found to be negative for C. pseudotuberculosis exposure by assay of CLA toxin antibody, were divided into four treatment groups. Each was shorn at either 0, 2, 4 or 8 weeks before dipping in a solution containing C. pseudotuberculosis. Blood samples were taken 6 weeks after dipping and sheep were slaughtered 12 weeks after dipping. A fifth smaller group of 14 sheep shorn 26 weeks before dipping, was also exposed to C. pseudotuberculosis and was slaughtered with the other sheep. RESULTS: The occurrence of caseous lymphadenitis abscesses did not differ between groups or with sheep shorn 26 weeks before dipping. The proportion of sheep that seroconverted to the C. pseudotuberculosis toxin and cell wall ELISA was larger in sheep dipped immediately after shearing than in sheep in the other groups. CONCLUSIONS: Delaying dipping until 8 weeks after shearing did not decrease the C. pseudotuberculosis infection rate due to dipping. Sheep dipped immediately after shearing developed higher concentrations of antibody to C. pseudotuberculosis than sheep when dipping occurred between 2 and 8 weeks and later after shearing.     

Preliminary observations on ticks and tick-borne diseases in the north west province of Cameroon. I. Babesiosis and anaplasmosis.

During a survey on ticks and tick-borne diseases in the North-Western Cameroon at the Bamenda cattle market, the ticks identified were Boophilus annulatus (20%) and B. decoloratus (80%). More than 50% of the ticks were collected during the dry season. Of 524 blood smears 47.3% were positive for Babesia bovis, 31.1% for B. bigemina and 2.2% for Anaplasma marginale. 19.4% were negative.