Evaluation of histopathological changes, viral load and immune function of domestic geese infected with Newcastle disease virus

Abstract

Outbreaks of Newcastle disease in flocks of geese with high morbidity and mortality in southern and eastern China have been reported frequently since the late 1990s, which broke the traditional view that geese are considered to be the natural reservoir of Newcastle disease virus (NDV) but show few or no clinical signs after infection. In this present study, geese were infected intranasally with a local strain of NDV. Clinical disease and gross pathology were observed. Serum and immune organs were collected from geese sequentially euthanized or after disease-associated death. We studied the histopathology of immune organs by haematoxylin and eosin staining and NDV fusion protein was detected in tissues by immunohistochemistry. At the same time, the SYBR Green I real-time polymerase chain reaction assay was used to detect the viral load from the collected samples. Serum samples were tested for NDV-specific antibodies and avian influenza virus (AIV)-specific antibodies by haemagglutination inhibition (HI) test. The results showed that severe lesions and numerous positive reactions of NDV antigen were detected in the immune organs. High viral loads developed in immune organs of infected geese, correlating with the severity of clinical signs and lesions in the tissues. Furthermore, the infected geese developed low HI antibody titres to both AIV and NDV. The present study showed that the replication and dissemination of the NDV isolate was widespread in immune organs of geese. The study revealed that waterfowl may not only be a natural reservoir of NDV but also become susceptible to disease and may play a major role in the epidemiology of Newcastle disease.

Pathobiology of Avian avulavirus 1: special focus on waterfowl

“…Amongst all genotypes of Class II, genotype I and II are the most prevalent genotypes in the waterfowl and have been isolated from many countries (summarized in Table 1). Waterfowl-origin isolates belonging to genotype VII of APMV-1 are constantly increasing especially in China, Republic of Korea, and Taiwan [16,[21][22][23][24][25][26][27][28][29][30][31][32]. These emerging outbreaks are increasing the global burden of APMV-1 and causes heavy economic losses [24].…”

“…Besides the strong innate immune responses, waterfowl are generally considered long-term carrier of APMV-1 and disease outbreaks have been reported since 1997 [12][13][14], and were confirmed by follow up experimental studies. Clinically and naturally infected ducks and geese with APMV-1 show clinical signs such as elevated body temperature, excessively excreted oral mucus, dried cloaca, watery, greenish-white diarrhea, vain attempts of eating and drinking, listlessness, anorexia, crouch, eyelid edema and emaciation [14,23,46,47]. Ducks may show up to 70% decrease in egg production, 80% morbidity and 67% mortality [15,48] however the mortality in ducks varies with the different breeds, virus strain and dose of virus [15].…”

“…Some birds also show weakness of legs and wing along with unilateral or bilateral incomplete paralysis and the effects of this paralysis increases with progression of the disease [46]. Duck and geese also show the neurological signs such as muscular trembles, muscular dis-coordination, circling, and twisting of head and neck [23,46,48]. These clinical signs disappear according to infection status; mildly affected recover sooner and severely affected birds may recover after 15 days of infection [22,46].…”

“…These clinical signs disappear according to infection status; mildly affected recover sooner and severely affected birds may recover after 15 days of infection [22,46]. APMV-1 infected ducks and geese show the gross lesions on the immune organs such as bursa, spleen, thymus, mild to severe tracheitis, kidney enlargement, necrosis of pancreas, congestion on the meninx and in the brain and diffuse brain edema, focal hemorrhages in the mucosa of the proventriculus and intestine (especially duodenum and upper part of jejunum) [14,22,23,46]. Bursal atrophy, hemorrhagic thymus and splenomegaly with white necrotic spots were found in the APMV-1 infected geese and duck [23,46].…”

“…APMV-1 infected ducks and geese show the gross lesions on the immune organs such as bursa, spleen, thymus, mild to severe tracheitis, kidney enlargement, necrosis of pancreas, congestion on the meninx and in the brain and diffuse brain edema, focal hemorrhages in the mucosa of the proventriculus and intestine (especially duodenum and upper part of jejunum) [14,22,23,46]. Bursal atrophy, hemorrhagic thymus and splenomegaly with white necrotic spots were found in the APMV-1 infected geese and duck [23,46]. These lesions and histopathological changes may be due to higher viral loads, multi-systemic distribution of the virus in these immune organs [23].…”