Distribution and abundance of goat lice (Phthiraptera: Bovicola spp and Linognatus stenopsis) on their host : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Zoology at Massey University

Abstract

The abundance and regional distribution of louse populations were examined by fleece-parting and post-mortem counts on 20 feralxangora and six saanenxangora goats. The effect of temperature on louse population dynamics was examined in a controlled-temperature experiment using the saanenxangora goats. They were divided into two groups, held at 10 or 25 degrees C and artificially infested bith Bavicola spp. Fleece-parting counts were made weekly for 16 weeks and a final count was made at post-mortem. Fleece characteristics of the 26 goats were measured. The distribution of Bovicola caprae and B. limbatus on all 26 goats, and of Linognathus stenopsis on the 20 goats is not uniform over the hosts body. Preferences for particular regions are apparent for the two Bovicola spp and L. stenopsis. The preferred sites for Bovicola spp are along and either side of the backline, while the preferred sites for L. stenopsis are the shoulder regions, chest and throat. Grooming may account for the observed distribution pattern of Bovicola spp, but it does not appear to be the most important factor for L. stenopsis. Fibre density appeared to affect the distribution of Bovicola spp females and eggs but not those of L. stenopsis. The two genera show different preferences for egg-laying sites and Bovicola spp uses a narrower range of fibre diameters for oviposition than L. stenopsis. The magnitude of louse populations varies markedly between goats. Most goats in this study are host to few Bovicola spp while only two have >10000 in the 26 body regions examined. Linognathus stenopsis is present in low numbers (<520) on all of the 20 feralxangora goats examined. Grooming efficiency, but not nutrition, may have caused the differential infestation levels. However, differential infestation is more likely to be influenced by genetic differences between hosts, resulting in skin exudates which are different chemically or in quantity for different goats. A build-up of lice under cool temperatures is not demonstrated in this study. Temperature is therefore probably not the critical factor influencing the build-up of louse populations on ungulates in winter, and their decline in summer. Counts of Bovicola spp by fleece parting techniques show good correlation with post-mortem counts, and can therefore be used to obtain a reliable estimate of louse infestation levels on individual hosts.