ORIGINAL ARTICLE Effects of Trypanosoma brucei infection and treatment on haematoserological response of West African Dwarf sheep to Brucella abortus vaccine C. A. Akpan 1 & N. E. Nweze 1 & C. C. Chukwu 1 Received: 26 May 2016 /Accepted: 8 August 2017 /Published online: 14 August 2017 # Springer-Verlag London Ltd. 2017 Abstract This study aims to investigate the effects of Trypanosoma brucei infection and treatment on haematoserological status of West African Dwarf sheep to Brucella abortus vaccine. Twenty-four adult WAD sheep of mixed sexes were randomly assigned into 6 groups of 4 each. They were either infected with 1 × 10 6 trypanosomes intrave- nously (groups 2–6) or uninfected (group 1). The different groups were treated as follows: group 2 (positive control—7 mg/kg diminazene aceturate (DA)), group 3 (7 mg/kg DA and 5 mg/ kg levamisole), group 4 (7 mg/kg DA and 50, 000 IU vitamin A), group 5 (7 mg/kg DA and 50, 000 IU vitamin A 3 weeks post infection), and group 6 (7 mg/kg DA and 5 mg/kg levamisole and 50, 000 IU vitamin A). All the animals were vaccinated with B. abortus S19 vaccine 2 weeks post infection (PI). Parameters assessed parasitaemia, total and differential white blood cell counts, and antibody titres to B. abortus antigen. Average prepatent period was 5 days. Trypanosomes were completely cleared from the bloodstream following treatment. There was no relapse parasitaemia recorded. By weeks one and two post infection, there was significant (P < 0.05) leucocytosis which was due to lymphocytosis and neutrophilia in all infected groups. There were no significant changes in monocytes, oesinophils, basophils, and antibody titres of both infected and uninfected sheep. Experimental T . brucei infection and treatment of WAD sheep caused significant (P < 0.05) leucocytosis 1 to 2 weeks PI due to lymphocytosis and neutrophilia, but no significant differ- ences in antibody titres to B. abortus S19 vaccine when compared with the vaccinated uninfected. Keywords Trypanosoma brucei brucei . Brucella abortus . West African Dwarf sheep . Haematoserology . Treatment Introduction Trypanosomosis is a haemo-parasitic disease affecting both man and animals. It poses a significant health challenge espe- cially in sub-Saharan Africa. African animal trypanosomosis (AAT) causes serious losses in cattle, sheep, goats, pigs, hors- es, and many other animals (Denbarga et al. 2012) by reducing milk production, weight gain, reproduction, and eventually death of the affected animals (Hoet et al. 2004). The disease leads to reduction of animal protein (Guilherme and Andre, 2011) thereby promoting food insecurity in the region (Abdulazeez et al. 2013). It contributes greatly to under devel- opment of sub-Saharan Africa (Oyewusi et al., 2010) through poverty. Besides causing disease, trypanosomes induce profound im- munosuppression (Tabel et al., 2008) which renders infected animals susceptible to secondary infections. Such animals have poor immune responses to bacterial and viral vaccines (Tabel et al., 2013) due to reduction of their ability to mount protective immune responses against invading parasites (Taylor and Mertens, 1999). Immunosuppression is a major obstacle to sus- tainable livestock production (Abebe, 2005) and food security. It is of particular significance in endemic areas where herd im- munity against serious epizootic diseases depends on massive vaccination campaigns (Murray et al., 1984). Trypanosomosis has been reported as one of the possible causes of vaccine failures due to the immunosuppression it produces (Tabel et al. 2013) in affected animals. Reports have shown depressed immune responses to anthrax spore vaccine in goats infected with Trypanosoma congolense (Mwangi et al., 1990) and haemorrhagic septicaemia vaccine in buffalo * C. A. Akpan nwakaego.nweze@unn.edu.ng 1 Department of Veterinary Medicine, University of Nigeria, Nsukka, Nigeria Comp Clin Pathol (2017) 26:1319–1327 DOI 10.1007/s00580-017-2533-0