The sheep tick,Ixodes ricinusL. Eradication by dipping sheep

Tick-induced blood loss leads to regenerative anaemia in the European hedgehog (Erinaceus europaeus)

Although there is an increasing understanding of the role of parasites in their host dynamics, accurate, quantitative estimates of parasite caused morbidity in wild animals are rare. Here, we examine the possible impact of 2 tick species (Ixodes ricinus, I. hexagonus) on the condition of the European hedgehog (Erinaceus europaeus). For this, we tested for correlations between blood parameters of 36 adult hedgehogs from an experimental population enclosed in a natural habitat and their tick infestation over a period of 8 months (March–October 2007). We found correlations between the tick infestation and the concentration of red blood cells, haemoglobin, haematocrit, MCH, MCHC, thrombocytes, lymphocytes and neutrophils. These results indicate that ticks can induce anaemia in the hedgehog. The peripheral blood characteristics and the erythrocyte indices characterize this anaemia as haemorrhagic and regenerative. During the course of our study the hedgehogs of our population showed below normal mortality but morbidity was found to be high resulting from the blood loss caused by the feeding activity of the ticks.

The quantity of blood imbibed by Hyalomma anatolicum anatolicum Koch, 1844 (Ixodoidea, Ixodidae)

1. The weight of blood ingested by all stages of H. anatolicum anatolicum has been determined and from the results a direct relationship appears to exist between the weights of replete adults and their blood content. In engorged nymphs the relationship was subject to some variations, while in fully fed larvae no such correlation was apparent, indicating the ingestion of a large proportion of extravascular fluids.

2. It was found that all instars concentrate the imbibed blood by the elimination of water. In larvae the concentration is by a factor of at least 5·25, in nymphs 3·4, in females 2·1 and in males 1·4.

3. A correlation was found between the external colour of fully engorged larvae and the quantity of blood imbibed.

I wish to thank Dr R. P. Chaudhuri for providing the original specimens of H. anatolicum anatolicum from which the culture was started, and Professor Don. R. Arthur for reading the manuscript and for his advice and assistance.