Atrophy of the lymphoid organs and suppression of antibody response caused by velogenic Newcastle disease virus infection in chickens

Abstract

This project was undertaken to study the immunosuppressive capabilities of velogenic viscerotropic pathotype of Newcastle disease virus (VVNDV) infection in cockerels. Two hundred six-week-old cockerels were divided into four groups. Groups B/VUC and C/VC were vaccinated with LaSota in drinking water at 6 weeks of age. Groups C/VC and D/UC were challenged with VVNDV at 8 weeks of age. Three days post challenge (PC), the cockerels in group D/UC came down with clinical signs which included depression and greenish diarrhoea. Total mortality was 74.6 %. The C/VC cockerels showed no clinical signs. But both challenged groups showed significant weight loss, significant loss of total serum proteins, globulin and albumen (P < 0.05). These losses were more severe in the D/UC than in the C/VC. There was severe atrophy of the bursa, spleen and thymus in both groups. Histopathology showed severe necrosis and depletion of the lymphocytes in the three lymphoid organs. However, the lesions were more severe in the D/UC than in C/VC cockerels. On day 28, PC groups B/VUC, C/VIC and D/UIC were revaccinated with LaSota. The haemagglutination inhibition antibody response on days 35, 42 and 49 PC was very low in groups C/VIC and D/UIC when compared with B/VUC cockerels. These observations show that VVNDV infection both clinical and subclinical can cause immunosuppression and vaccine failure due to severe destruction of the lymphocytes in the lymphoid organs. This will be a serious problem for poultry production in those countries where the disease is enzootic.

Low dose velogenic viscerotropic Newcastle disease virus infection caused 30% mortalities in Anak broilers but none in Lohmann Brown layer chickens

“…This obviously led to serious loss of some viral particles and the production of abnormally low mortalities of 0 and 30% in the layer chickens and broilers respectively. In our earlier experiments using this same virus at median embryo effective of 10 6.1 to 10 8.46 after 2-3 days storage at −40°C, we had mortalities of 76-100% in chickens and 60% in turkeys (Igwe et al 2014;Okpe et al 2015;Ezema et al 2016;Okoroafor et al 2017). Wakamatsu et al (2006) studied different strains of vvND virus infection in 4 and 6 weeks old chickens and reported 100% and 92% mortalities respectively.…”

“…There is severe atrophy of the lymphoid organs with severe necrosis and depletion of lymphocytes in the bursa, spleen and thymus (Igwe et al 2014;Okoroafor et al 2017). This may lead to immunosuppression (Ezema et al 2016). The histopathology of the velogenic viscerotropic ND (vvND) shows that the lymphocytes are the major cells that undergo necrosis just as in infectious bursal disease (IBD) (Brown et al 1999;Kommers et al 2002).…”

Response of cyclophosphamide-treated broiler chickens to challenge with velogenic Newcastle disease virus

“…One major impetus for this work is the striking similarities between the lesions of vND and those of infectious bursal disease (IBD) of chickens. In both diseases, there are proventricular haemorrhages, caecal tonsil haemorrhagic ulcers, enteritis and severe atrophy of the bursa, spleen and thymus due to severe necrosis and depletion of the lymphocytes in the lymphoid organs (Okoye 1984;Mahgoub 2012;Ezema et al 2016;Sá e Silva et al 2016). In fact, in both diseases, the lymphocytes are the major cells that are destroyed.…”

“…IBD suppresses humoral antibody response in surviving chickens (Okoye 1984;Hoerr 2010;Mahgoub 2012). Evidence that vNDV infection is also immunosuppressive is gradually emerging as Ezema et al (2016) reported that experimental vNDV infection suppressed HI antibody response to La Sota vaccination in surviving chickens. It becomes interesting to find out if like in IBD the lymphocytes play any role in the establishment and severity of vNDV infection.…”

“…These vaccines can protect birds from the disease but cannot prevent them from becoming infected, shedding the virulent virus in their faeces and transmitting it from infected to healthy birds, and drop in egg production in laying hens (Ezema et al 2016;Igwe et al 2017). Therefore, ND outbreaks are still common in commercial vaccinated flocks despite the advances in vaccination against the disease (Dortmans et al 2012).…”