Aspects of the bio-ecology of the biting louse, Damalinia Limbata

[摘要] English: Biting lice are well known ecto-parasites of vertebrates. Most wild and domesticated animalshave one or more louse species, living on them. Although lice are a source of irritation to thehost, they are not generally considered as economically important because they do not causemuch physical damage. The sheep biting louse (Damalinia avis) has, however, been shown tocause losses in wool production and quality. Damalinia limbata are ecto-parasites on Angoragoats and can cause the same type of losses to the farmer as the sheep biting louse. Very littleresearch has been done on these lice and their impact on mohair production can therefore not beobjectively assessed.The objectives of the current study were to investigate aspects of the biology and distribution ofD. limbata and to promote more effective and economical management of these lice oncommercial farms. The following were investigated: (1) Aspects of the morphology of D.limbata and D. avis. (2) Environmental temperatures prevalent on the body of Angora goats. (3)The number of nymphal instars of D. limbata. (4) Seasonal changes in the populations of D.limbata. (5) The influence of D. limbata on the body mass of Angora goats and the productionand quality of mohair, as well as the efficacy of different control methods.Field experiments were conducted on the farm Preezfontein (29°50'S, 25° 19'E), situated 10 kmfrom the town Fauresmith, about 130 km southwest of Bloemfontein in the south-western FreeState. The veld type of this area is defined as 'False Upper Karoo' and falls in the Karoo biorne.The Free State is a summer rainfall region with an average precipitation of 450-500 mm perannum, with hot summers and cold winters and droughts occurring regularly.D. limbata and D. avis were compared using general morphological characters, morphometricmeasurements of various body regions and placement of dorsal and ventral abdominal sclerites.D. limbata has a more robust appearance than D. avis. Females of both D. limbata and D. aviswere on average 1.611 mm long and the males had average lengths of 1.378 mm and 1.255 mm,respectively. Male D. ovis had solid dorsal plates where as D. limbata males had dorsal plates,which were transversally split, on segments IV and V.Temperature studies, on the micro-habitat of D. limbata, showed that the temperature against theskin of an Angora goat is relatively constant at approximately 35°C. All attempts to establish alaboratory colony of D. limbata were unsuccessful.D. limbata was found to have three nymphal instars before reaching adulthood. Instar 1 hadaverage head-capsule widths and lengths of 0.252 mm and 0.202 mm, respectively. The secondand third instars had head-capsule widths of 0.364 mm and 0.467 mm and lengths of 0.305 mmand 0.425 mm respectively.The louse populations increased during spring and early summer, peaking in mid summer. Midwinter shearing seemed to have a greater impact on the louse populations than mid summershearing. D. limbata moves around the body of Angora goats, being more abundant on theventral areas of the body during summer and more evenly dispersed over the body during winter.It was found that D. limbata does not have an adverse influence on the body mass of Angoragoats, but does adversely affect mohair production and quality. The average loss in mohairproduction was 12 % and individual losses of as much as 25 % were recorded, representingsubstantial financial losses to the farmer. D. limbata was effectively controlled by Deltamethrinwhen applied as either a backline treatment or as a lateral application with a Tikspray applicator.

[发布机构] University of the Free State