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PubMed1976

Factors affecting the detection of infestations of Boophilus microplus in tick control programs.

Factors affecting the probability of detecting infestations of Boophilus microplus when herds of cattle are examined were studied. The probability of detecting a tick depends on the number of infested cattle in the herd, the probability of ticks being present on the areas of the beast examined, the efficiency of the examination and the proportion of the herd examined. A mathematical expression relating these factors was derived, and a range of values calculated to demonstrate the relative importance of each factor. It was evident that the efficiency of the examination should be kept better than 75%, and that it is necessary to employ a high sampling rate, preferably 100% of the herd. The probabilities of ticks being present on 6 predilection sites and 4 combinations of sites of an infested animal were determined experimentally. The tail butt, esutcheon, belly, dewlap and to a lesser degree neck and ear were all very suitable sites on which to find cattle ticks. A combination of tail butt, escutcheon and neck produced probabilities (0.58 and above) considered adequate to form the basis of an examination system. Examination systems used in New South Wales, Queensland, Argentina and at the United States-Mexico border are described. As a result of this study a new standardised system has been adopted by the Board of Tick Control for use by all New South Wales inspectors.

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PubMed1989

Effect of tick control on liveweight gain of cattle in central Zambia.

Field trials were carried out during 1982-86 in two different ecotypes in central Zambia to determine the impact of tick control on the liveweight gain (LWG) of cattle. During the first 2 years of the trial a diamidide acaricide (Amitraz) sprayed at weekly intervals caused periodic depression in LWG in young animals. Thereafter a pyrethroid acaricide (cypermethrin) was used. During the 1984-85 tick season infestations of 50-120 adult Amblyomma variegatum Fabricius in untreated animals caused significant reductions in LWG. From the differences in LWG between treated and untreated cattle, the induced loss in LWG was estimated at 46-61 g per engorged female A.variegatum.

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PubMed1991

Re-assessment of tick control after immunization against East Coast fever in the Eastern Province of Zambia.

East Coast Fever, caused by the protozoon Theileria parva and transmitted by the ixodid tick Rhipicephalus appendiculatus is one of the most important cattle diseases in east and central Africa, responsible for considerable direct losses and necessitating expensive control measures. Traditionally, the disease was controlled by means of intensive tick control. The Belgian Animal Disease Control Project was requested to study the disease epizootiology and vector ecology in order to formulate and implement a control program adapted to the requirements and capabilities of the cattle owners in the Eastern Province of Zambia. The weaknesses of a rigorous tick control program were demonstrated. It was decided to initiate an immunization program in the enzootic areas. The overall calf mortality rate was lowered by 90% and it was shown that none of the other tick-borne diseases caused significant problems in the absence of tick control. The tick ecology studies had indicated that the climatic conditions in the area were so unfavourable that the important vector species (Amblyomma variegatum, Boophilus microplus and R. appendiculatus) would not attain problem levels. It was therefore recommended to suspend all tick control in the area. Control of East Coast Fever in the epizootic and disease-free areas is still a more complex issue. It appears unlikely that the latter will remain disease-free, because of the proximity of the enzootic areas and because of considerable cattle movement in the province. Given the advantages of control by immunization, it can be argued that a longterm solution should be based on this approach.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1985

Changes in cattle tick control practices in south eastern Queensland from 1977 to 1982.

Results of a survey of cattle producers in south eastern Queensland in 1982 concerning cattle tick control have been compared with those of a similar survey carried out in 1977-78. During the interval between these surveys the proportion of beef farms with tick resistant (Bos indicus infusion) cattle as the main breed had increased from 47.8% to 60.0%. Chemical control methods had improved but many producers were continuing to treat their cattle more often than necessary. Over the period there was an increase in the proportion of farms with small numbers of animals, and 30% of the farms had less than 50 cattle.

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PubMed1980

The relevance of different test methods for the evaluation of tick controlling substances.

Results of comparative investigations of different in vitro and in vivo procedures are reported. The aim of the investigations was to determine which of the test methods gives the best estimate of the activity against ticks under field conditions when used for active ingredients of varying chemical constitutions and different types of action. The data obtained indicate that results of in vitro test methods using tick larvae differ with the test procedure employed and the chemical class of the active ingredient. Therefore, in many instances these test methods do not allow extrapolation to practical conditions. In vitro tests employing engorged female ticks are much more reliable for most classes of compounds. However, there still are groups of compounds for which this test furnishes incorrect predictions. A better indication of the potency of a compound is therefore obtainable using in vivo test procedures. An economic and reliable method for the selection of prospective active ingredients is the mini-dip method using the specific host animal. This method provides not only an indication of the future concentration to be recommended but also provides information on the different types of activity of compounds active against ticks, i.e. tickicidal effect, paralysis, detachment, inhibition of development. Such observations are difficult or even impossible when in vitro methods are employed. The predictive value of the mini-dip method has been established for tick controlling substances of widely varying chemical constitution like organophosphorus compounds, carbamates, thioureas, diamidides, thiazolines and synthetic pyrethroids.

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PubMed1983

The economics of cattle tick control in dry tropical Australia.

The economics of strategic dipping compared to nil treatment of cattle ticks (Boophilus microplus) on Droughtmaster cattle was assessed using a partial budget analysis. The analysis was based on reported experimental data which showed a bodyweight gain advantage from strategic dipping of 45 kg/head for growing cattle and 35 kg/head for breeding cows. Costs of dipping were calculated using 3 acaricide costs, that is 5.9, 20.9 and 62.7 per head and allowances were made for mustering, maintenance of facilities and annual cost of asset purchase under an intensive farm management system similar to the reported experimental conditions. The net gain of benefits over costs per annum for each acaricide cost was $927, $810 and $483 per 100 breeders and their progeny. Breakeven beef prices at which it was worth dipping were found to be 61, 69 and 94 per kg dressed weight depending on the cost of acaricide used for dipping. All prices and costs are expressed in 1981 dollars of purchasing power.

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PubMed1975

Some aspects of the ecology and lifecycle of Amblyomma cajennense (Fabricius 1787) in Trinidad and their influence on tick control measures.

The distribution in Trinidad of the tick Amblyomma cajennense is defined, and the methods used to determine the boundaries of the infested areas are outlined. The relationships between climate, vegetation and husbandry methods and the distribution of the tick are described. Monthly tick collections from specific animals to determine exact seasonal variations were not possible but a study was made of the normal life cycle under laboratory conditions, the results being used to assist in interpreting the field picture and formulating methods of control. Possible systems of control are outlined and mention is made of the feasibility of eradication of the species in Trinidad.

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PubMed1980

A survey concerning cattle tick control in Queensland. 3. Chemical control.

Survey results concerning chemical control of the cattle tick (Boophilus microplus) in Queensland are reported in detail, and differences due to region, breed and type of enterprise are discussed. The results show that chemical control was more intensive in Zebu and Zebu crossbred cattle than could be justified economically and that a minority of producers with European cattle carried out strategic dipping. Owners of plunge dips did not make regular use of testing facilities, available from the Department of Primary Industries or the chemical companies.

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PubMed1992

Immunisation of cattle against theileriosis in Nakuru District of Kenya by infection and treatment and the introduction of unconventional tick control.

One hundred and one cross European-Boran cattle (50 cows and 51 calves), on a farm in Nakuru District, Kenya, were immunised against theileriosis using Theileria parva lawrencei and Theileria parva parva stocks from another district of Kenya. The stabilates used were T.p.lawrencei (Mara III) used at 10(-1.7) dilution and T.p.parva (Kilae) used at 10(-1.0) dilution. The stabilates were combined and inoculated simultaneously with a short-acting formulation of oxytetracycline hydrochloride given intramuscularly at 10 mg kg-1 body weight and was repeated on Day 4 after inoculation of the stabilate. Most of the theileriosis challenge on the farm was thought to be derived directly from the African buffalo (Syncerus caffer). Nine percent of the cattle had significant indirect fluorescent antibody (IFA) titres before the immunisation and 99% after immunisation. The immunised cattle were exposed to tick-borne disease challenge on the farm by withdrawal of acaricide cover. The immunised cattle were divided into five groups plus two susceptible control cows and two calves for each group. Cattle in four of the groups had acaricidal ear tags, each group having a different type, applied to both ears and the fifth group remained untagged. The animals remained without conventional acaricide application for 134 days. Ten out of 20 (50%) non-immunised control cattle became T.p.lawrencei reactors which only one out of 97 (1%) of the immunised cattle reacted. A frequent complication noted was mild infections due to unidentified Theileria sp. which required expert differentiation from T.parva infections. An additional group of ten steers whose tick load was removed by hand at weekly intervals was introduced 79 days after exposure; these had no tick control and four became T.p.lawrencei reactors. Of 12 calves born during the exposure period and without tick control, four became theilerial reactors and one died. The application of acaricidal tags however, reduced tick infestation levels considerably compared with untagged controls but did not prevent transmission of theileriosis with the possible exception of tags on Group 4. A number of transient low grade fevers were noted and attributed to Theileria sp., Ehrlichia bovis, Ehrlichia (Cytoecetes) ondiri and Borrelia theileri infections, none of which were fatal. One immunised animal died of acute dual infection of Babesia bigemina and Borrelia theileri after acaricide control by spraying was re-introduced but no Anaplasma infections were detected. An analysis of the economic effects of immunisation was made.

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PubMed1990

The impact of pure infestations of Rhipicephalus appendiculatus and Amblyomma hebraeum on the productivity of cattle and implications for tick control strategies in Africa.

This paper reviews studies carried out by an FAO project in Zimbabwe, on the effects of the ticks Rhipicephalus appendiculatus and Amblyomma hebraeum on the productivity of cattle. Larvae and nymphs of the two species had no detectable effect on liveweight gain (LWG). The losses in LWG caused by each adult female that completed feeding were approximately 4 g for R. appendiculatus and 10 g for A. hebraeum. Losses in milk production caused by both species amounted to approximately 7 g for every female that engorged. The loss in productivity per engorged female, known as the damage coefficient, can be used in simulation models to estimate the value of production losses caused by the ticks and the economic benefits of control strategies.

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