| dc.description.abstract | Anaplasma phagocytophilum, an intracellular, gram-negative bacteria, survives and replicates in neutrophilic granulocytes (Stuen et al. 2013). The disease it causes is called granulocytic anaplasmosis which can affect many vertebrate animals, including sheep, horses and also humans (Goldman & Green 2009). I. ricinus, which is widespread in Europe, is the most common tick known as a vector for this disease (Stuen et al. 2013). A. phagocytophilum mainly cause fever which lasts for 1-2 weeks (Stuen & Longbottom 2011). Other clinical signs are mild thrombocytopenia (Carrade et al.), reduced weight gain (Stuen et al. 2002), rigors, headache, myalgia and malaise (Goldman & Green 2009).
This study was designed to achieve two goals. At first, the aim was to investigate if Dermacentor reticulatus and Amblyomma hebraeum were, besides I. ricinus possible vectors for the transmission of A. phagocytophilum. D. reticulatus is the main vector of Babesia canis and other piroplasm species (Karbowiak 2014) and is distributed in many parts of Europe (from Atlantic ocean to Kazakhstan), particularly in wooded areas (Wall & Shearer 1997; Taylor et al. 2007). Amblyomma hebraeum is distributed in the rural areas of southern Africa (including South-Africa, Zimbabwe and Mozambique) and is known as the vector of Rickettsia africae which is known as ‘’African tick bite fever’’ (Mabey et al. 2013). If the transmission of A. phagocytophilum by A. hebraeum and D. reticulatus can succeed, there is a significant possibility for the occurrence of A. phagocytophilum in A. hebraeum and D. reticulatus in areas of the world where these ticks are common (southern Africa and Western-Europe).
The second goal was to determine if blood samples from different animals coming from different areas in the Netherlands or faeces (tested positive for A. phagocytophilum) from infected ticks will cause the same symptoms in sheep and contain the same strain of Anaplasma phagocytophilum. These products were injected in individual sheep.
In this study, three experimental rounds were designed to investigate the two main goals. Each experimental round (which lasted 14 days) contained four sheep which were each exposed to A. phagocytophilum differently under laboratory conditions. The sheep were monitored by daily temperature measurement and if fever was measured, blood was collected and examined by making blood smear (to see if inclusion bodies/morulae were present in the neutrophil granulocytes) and by performing a PCR/RLB. Ticks were collected when they were engorged or at the end of the experimental round. When they were fed on a sheep which had a febrile period, they were tested to determine their infection rate.
Transmission of A. phagocytophilum did not succeed in D. reticulatus and A. hebraeum. The sheep did not get any symptoms, so blood collection was not implemented. I. ricinus did successfully transmit A. phagocytophilum, which proves that the experimental model was accurate. Why transmission did not occur, is not clear yet, so further research is necessary.
The experimental round in which the second hypotheses was tested, showed that all the sheep injected with the different blood samples did get symptoms which were all similar to each other. After PCR/RLB, different strains of A. phagocytophilum were found in the blood. The sheep who was injected with the infected tick faeces did not develop any symptoms, so no blood was collected. | |
