Preventing ticks' harmful effects on livestock
Ticks are recognised as important ectoparasites of livestock, and incriminated as voracious blood suckers resulting in low productivity and mortality.
These affect the appetite, body condition, blood composition and respiratory rate of animals besides spreading tick-borne diseases. Although its burden is not found directly associated with reproductive efficiency, there is a trend that the time from parturition to first ovulation and to conception increase with an increase in tick burden.
Severe infestation has a negative effect on the reproductive efficiency of cattle.
These are harmful to livestock which includes irritation and allergy, udder wounds, myiasis, severe toxicosis and paralysis of the area. Having long and massive hypostomes (amblyomma and to some extent hyalomma) ticks may induce abscesses due to secondary bacterial infection.
In certain tropical regions, amblyomma variegatum adults are reported to cause severe bovine dermatophilosis which prevents upgradation of local cattle with highly susceptible imported breeds.
Some short hypostome ticks (boophilus) when present in large amounts may also cause devaluation of skins and hides due to bites. It is an economic problem for cattle producers owing to severe damage of external ear caused by feeding adult ticks. The irritated animals due to severe infestation try to relieve themselves by vigorous licking of the affected areas (self-licking).
It is found that high tick burden is correlated with low weight gains depending on the breed of cattle. Compensatory weight gains in all breeds at the end of winter might be associated with the decreased tick burdenon. Diseases associated with chronic tick-borne infestation can often lead to abortion, decreased weight gain and lowered milk production in livestock.
In economically depressed regions, chronic disease in livestock can also result in severe consequences including malnutrition and starvation.
The global warming has resulted in the establishment of ticks even at higher altitudes in the past decade. In tropical and sub-tropical countries, including Pakistan, the higher infestation rates of ticks are reported in summer-from May to August.
Breed is considered an import determinant in the susceptibility of animals to tick infestation. Resistance or the capability of developing an effective immunological response to tick infestation is genetically determined.
In Pakistan, pure-bred Sahiwal cows are less susceptible to tick infestation than other European breeds like Jersey, Friesian and their crosses (personal observation).
Control and prevention strategies can be achieved by the development of tick research, including new acaricide approaches or tick resistance cattle, and vaccination.
Acaricide treatment remains the cornerstone for controlling ticks and tick-borne pathogens affecting cattle in developing countries in the absence of effective vaccines or (in majority of cases) a cold chain to supply them.
Epidemiological investigations have suggested that reduction in acaricide-treatment frequency to permit high tick-attachment rates allow the development of endemic stability. Chemical control may have its residual effects in milk and meat of animals and cause environmental pollution. Moreover, these chemicals are costly and require foreign currencies, thus constituting a major economic loss to the livestock industry.
Grooming is found effective in controlling ticks. Oral and scratch grooming significantly increased from baseline during tick seeding and declined following the removal of ticks with acaricides. Poultry and wild birds especially crows are considered a good source of biological control of cattle ticks.