[Evaluation of the DDT residue content in the grass cover after tick control treatments in taiga foci of tick-borne encephalitis].
Explore the source record for details and available documents.
SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Explore the source record for details and available documents.
The results of a survey on tick control carried out in 1977-78 indicate that tick resistant cattle have been introduced for their heat and drought tolerance and their ability to grow more rapidly than European cattle, especially in the extensive grazing country of Northern and Central Queensland. In South-eastern Queensland acceptance of tick resistant cattle has been slower because producers believe they are more difficult to manage than European cattle. A need for more publicity to be given to the different handling methods required by these animals was shown. Some producers cull their less resistant crossbred Zebu cattle and others could be encouraged to do so. Pasture spelling appears to be quite common especially in the Costal North; it is being carried out for pasture management rather than as a tick control measure. Producers in Central and South-eastern Queensland, who do not spell pastures, feel that it reduces the carrying capacity.
A survey conducted in 5 magisterial districts involving rapid rural appraisal and a questionnaire showed participation in state-managed and funded dipping programmes by cattle owners in communal areas of the central Eastern Cape to be nearly complete, with 98% of livestock owners interviewed participating in all dipping events. Disease control was the main reason for participation, but farmers perceive dipping to have a much broader disease-preventing activity than is really the case. Other reasons for participation in dipping programmes were to prevent ticks from sucking blood, provide animals with a clean appearance, and prevent damage to teats of cows. many livestock owners complement dipping with other tick control measures, including old motor oil, household disinfectant, pour-on acaricide and manual removal of ticks. Recently local farming communities were given the responsibility of buying dipping acaricide. This has presented them with the challenge of developing farmer-managed, cost-effective tick control programmes. At present, this process is constrained by lack of information and farmer training.
The possible use of chickens as predators of livestock ticks was studied. Chickens were allowed to scavenge for 3 h among tick-infested cattle in a typical township backyard during the milking period. Boophilus decoloratus, Hyalomma marginatum rufipes, Rhipicephalus evertsi evertsi and Otobius megnini were recovered from the crops and gizzards at necropsy. The numbers of ticks ingested ranged from 0-128, with an average of 28.81 (+/- 8.42) per chicken. This study has confirmed that chickens are natural predators of livestock ticks and that chickens can be used as part of an integrated tick control plan in urban cattle-management systems in resource-poor communities in South Africa.
Of six grass species analysed, Melinis minutiflora (molasses grass) showed the highest anti-tick deterrent properties while Andropogon gayanus (Gamba grass) exhibited the ability to maintain a defined, constantly low, initial host tick infection property and lengthy but low to moderate field tick population. It was concluded that Melinis minutiflora is a species which would best be used in a tick control package within a marginal tick zone while Andropogon gayanus has the advantage within an endemic tick zone.
Tick and fly control programmes have undergone radical review in recent years. Insecticidal control measures are now often seen as a means of reducing target populations to a level sufficiently low for final eradication by biological or ecological techniques, the sterile male method (SIRM) being particularly favoured. As a preliminary, the new range of insecticidal application techniques includes insecticidal tags, bands, blouses, implants and pheromone baits. The final eradication programme could then involve the use of sterile flies or sterile hybrid ticks, for example. Immunization of cattle against ticks, the use of tick-resistant crossbreeds of cattle, tick-repellent grasses and dung burying beetles are among the additional techniques now being actively investigated.
The effectiveness of three tick control regimes on the occurrence of Amblyomma variegatum and dermatophilosis on cattle on the coastal plains of Ghana were compared. Animals at one kraal were sprayed with amitraz at predilection feeding sites of ticks every second week using a high concentration minimum volume technique. Animals at two other kraals were treated with a deltamethrin based pour-on acaricide; at one kraal it was applied once every month while at the other kraal it was used at strategic times based on the expected seasonal increases in the level of infestation with A. variegatum. Animals in a fourth kraal (control group) were treated, by the herdsmen, to control excessive tick build-up as practised under traditional management systems. Fortnightly treatment with amitraz reduced the level of infestation with A. variegatum and the prevalence of dermatophilosis dropped to a low level. The pour-on acaricide similarly depressed the prevalence of dermatophilosis.
The performance of Nguni, Bonsmara and Hereford oxen which were maintained free of ticks by short interval treatment with acaricide irrespective of tick load (tactical) was compared with similar groups which were treated for tick infestation only when the numbers of adult ticks on the cattle increased to moderately high proportions (strategic). Strategically treated Nguni oxen acquired a strong resistance against ticks and showed weight gains comparable with the tick free Nguni group. Weight gains in the Bonsmara group were higher in the strategically treated group suggesting a possible effect of the acaricide on the tick free group. Strategically treated Hereford oxen acquired heavy tick burdens and performed poorly compared with the tick free group. Practical approaches to strategic tick control under African conditions are discussed.
Sixty male weaner cattle at the National Range Research Station, Kiboko, Kenya were placed in four groups of 15 animals under four different tick control regimens for 16 months. The treatment groups were: spraying with acaricide weekly, spraying every three weeks, spraying whenever group mean tick infestations reached more than 200 per animal (once only in the course of the study) and a control unsprayed group. The cattle were weighed monthly. There were no significant differences between the liveweight gains of the groups during a period of severe drought and during the following period of compensatory weight gain. The untreated group gained more weight than the other groups. Cattle died in all groups, but without significant differences between the groups; the long drought and associated malnutrition were the prime cause of death. Rhipicephalus pravus and R pulchellus were the dominant tick species with fewer Amblyomma gemma, Hyalomma truncatum and small numbers of Boophilus decoloratus and R evertsi. These ticks transmit anaplasmosis, babesiosis and cowdriosis in the study area. Total tick counts reached 750 on individual animals but group means rarely reached more than 200 because of high resistance to ticks in some animals. Host resistance ranking within groups was virtually constant throughout the experiment. The study showed that intensive tick control is not required in the semi-arid areas of Africa.
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.
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.
A '4-poster' device that attracts white-tailed deer to a bait source, and as they feed, allows a self-application of a pesticide to the head, ears, and neck to control ticks was designed, constructed, and tested. The device consists of a central bin containing bait to attract deer and two feeding and application stations. These stations each have one bait port and two vertical pesticide-impregnated applicator rollers. This design allows unrestricted vertical retraction of the head to minimize injury to the deer or damage to the posts supporting the pesticide application rollers. Observations using deer demonstrated ready acceptance and repeated use by both antlered and antlerless deer. Results of an initial trial indicate that control values for lone star ticks, Amblyomma americanum (L.), exceeded 92-97% on deer that used the device regularly.
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)
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.
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.
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.
Explore the source record for details and available documents.
Explore the source record for details and available documents.