The effects of the abortifacient parasite, Neospora Caninum on Bovine Foetuses in early and late gestation



The effects of the abortifacient parasite, Neospora Caninum on Bovine Foetuses in early and late gestation. PhD thesis, University of Liverpool.

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Abstract

Neospora caninum is an obligate intracellular protozoan parasite, which is the most frequently diagnosed abortifacient in dairy cattle in the UK and is a leading cause of abortion worldwide. Neospora caninum infection in early gestation is associated with foetal death whereas in late gestation, infection can result in the birth of asymptomatic, but persistently infected animals. How the parasite kills the foetus is not fully understood, but it has been suggested that more mature foetuses are better able to mount a stronger immune response to control parasite multiplication and dissemination. The ability of the bovine foetus to respond to various antigens develops in a sequential fashion during the gestation period and foetal immunocompetence starts to develop at approximately 100 days gestation age (dg), but can only fully recognise antigens during mid-gestation at around 150 dg. Chapter 2 assessed the pathological effects of N. caninum on bovine foetuses in early and late gestation (70 and 210 days gestation, respectively) and also in foetuses from naturally infected dams after recrudescence of N. caninum in mid to late gestation. Based on results of an initial histological screen of 35 bovine foetuses and 2 new-born calves, a total of 12 foetuses and calves were selected and subjected to more detailed histological examination. Both haemolymphatic and non-haemolymphatic tissues were used. The distribution of N. caninum antigen, CD3-positive T cells, PAX5-positive B cells, monocytes/macrophages and neutrophils (myeloid/histiocyte antigen/calprotectin-positive), antigen presenting cells (MHCII), interferon gamma (IFN-γ) expressing cells, PCNA-positive proliferating cells and apoptotic cells (cleaved caspase 3-positive) was analysed by immunohistology. In uninfected, control foetuses in early gestation (90 days gestation), haemolymphatic tissues were moderately developed and exhibited normal morphological features with low lymphocyte turn over and no evidence of IFN-γ production. Uninfected foetuses in late gestation had fully developed haemolymphatic tissues with high lymphocyte turnover, indicative of a mature immune system. In the infected foetuses in early gestation, extensive apoptosis of lymphocytes was observed in the thymus and spleen compared to controls (p

Item Type: Thesis (PhD)
Additional Information: Date: 2014-07 (completed)
Depositing User: Symplectic Admin
Date Deposited: 10 Feb 2015 10:27
Last Modified: 17 Dec 2022 00:48
URI: https://livrepository.liverpool.ac.uk/id/eprint/2002404