Hemorrhagic enteritis in turkeys: purification and quantification of the virus

Two methods for purifying the virus of hemorrhagic enteritis from infected turkey spleens are described. One procedure utilized precipitation with polyethylene glycol, and the other consisted of trichlorotrifluoroethane extraction. Both procedures included sucrose-cesium chloride gradient centrifugation in the final purification step. The buoyant density of the viral fraction was 1.34 g/cm3, typical for adenoviral particles, and the size and morphologic characteristics of the virions observed by transmission electron microscopy suggested that the purified virus belongs to the family Adenoviridae. The biologic activity of the purified virus was titrated by inoculating 10-fold dilutions of the viral suspension into turkey poults. Mortality and hemorrhagic diarrhea proved to be inconsistent parameters of infection, and the degree of splenomegaly was proportional to the virus dose. The body/spleen ratio was the parameter selected for measuring viral activity, and the body/spleen ratio 50% was adopted as the unit for the titration of the virus. By using the same system it was demonstrated that the infectivity of the virus could be neutralized with antiserum produced in turkeys.     

Hemorrhagic enteritis of turkeys in California: serologic study of hemorrhagic enteritis virus antibody with an enzyme-linked immunosorbent assay

The incidence of hemorrhagic enteritis (HE) infection in California turkeys was studied by testing 2220 turkey blood samples from 173 flocks for HE virus (HEV) antibody by the enzyme-linked immunosorbent assay (ELISA). Maternal antibody was detected at 1 day of age in all flocks tested, and it vanished after 3 weeks. Acquired HEV antibody appeared at 8 to 10 weeks, and 100% of the meat and breeder turkey flocks were positive after 11 weeks of age. HEV infection occurred earlier in the meat flocks than in the breeder flocks, and it also occurred earlier during summer than during the fall and winter months.     

Hemorrhagic enteritis of turkeys: influence of maternal antibody and age at exposure

The effect of maternal antibody (MAB) to hemorrhagic enteritis (HE) on the response of turkeys to infection with virulent and avirulent strains of HE virus (HEV) was examined. The influence of age at exposure and treatment with HEV antibody on development of clinical HE also was studied. MAB protected poults from clinical HE for up to 6 weeks of age. MAB also interfered with vaccination against the disease for at least 5 weeks after hatching, as indicated by absence of HEV antigen in spleens and by poor seroconversion at 6 days and at 3 weeks post-vaccination, respectively. The incidence of clinical HE in MAB-negative poults was significantly higher in poults inoculated with virus at 15 days of age or older than in poults inoculated at 1-13 days of age. Further, MAB-negative poults embryonally inoculated with virulent or avirulent strains of HEV did not develop disease; these poults developed antibody and resisted challenge with virulent virus at 6 weeks of age. Poults treated with HE antibody within 1 hour of challenge or at 1, 3, or 5 weeks before challenge with virulent virus were protected against lesions and mortality induced by HEV. These results suggest that MAB may influence susceptibility of turkeys to infection with HEV for at least 5 to 6 weeks after hatching, unlike the case with most other viral infections of poultry. The results confirm that early age resistance to clinical HE is independent of MAB and suggest that such resistance persists for up to 13 days of age. The data also suggest that turkeys lacking MAB can be immunized against HE by embryo vaccination.     

Pathogenesis of canine parvovirus enteritis: sequential virus distribution and passive immunization studies

After oral inoculation, the sequential distribution of canine parvovirus was studied in 14 nine-week-old seronegative beagle dogs. Two or three dogs were necropsied on days 1 through 6 after inoculation. Tissues were collected for virus isolation, immunofluorescence testing, and light microscopy. Virus was isolated from, and fluorescent cells were seen in the tonsil, retropharyngeal and mesenteric lymph nodes one and two days after inoculation. Virus infection of systemic and intestinal lymphoid tissues occurred as early as three days after inoculation and was associated with viremia. Intestinal epithelial infection was first seen four days after oral inoculation. All dogs were viremic before intestinal epithelial infection was found. Fecal virus excretion first occurred four days after oral virus inoculation. Intestinal virus infection and lesions became progressively more severe between four and six days after inoculation. The severity of intestinal lesions was variable and related to the severity of systemic lymphoid tissue lesions and the magnitude and duration of viremia. Four littermates of virus-infected dogs were passively immunized against canine parvovirus with convalescent canine serum 24 hours after oral virus inoculation. Neither clinical signs, lymphopenia, nor fecal virus excretion occurred in passively immunized dogs. Intestinal epithelial infection was not demonstrable by immunofluorescence testing when passively immunized dogs were necropsied four, five, and six days after virus inoculation.     

Role of splenectomy in prevention of hemorrhagic enteritis and death from hemorrhagic enteritis virus in turkeys

Hemorrhagic diarrhea, gross hemorrhagic enteritis, and death caused by intravenous virus injection of hemorrhagic enteritis virus (HEV) were prevented in otherwise susceptible turkey poults by surgical splenectomy. The splenectomized poults produced anti-HEV antibodies, which indicated that splenectomy did not completely prevent replication of the virus. These results indicate that the spleen is necessary for the development of the intestinal lesions of this disease. The role of a toxic factor in this disease is discussed.     

火鸡出血性肠炎

出血性肠炎(HE)是幼龄火鸡的一种急性病毒性疾病,特征是突然发病,血便,死亡率不定,通常为高死亡率,还可以引起免疫抑制。血液从泄殖腔流出(图1),可在粪便中见到新鲜血液或黑粪症(图2)。     

Haemorrhagic enteritis of turkeys

出血性肠炎(HE)是幼龄火鸡的一种急性病毒性疾病,特征是突然发病,血便,死亡率不定,通常为高死亡率,还可以引起免疫抑制.血液从泄殖腔流出(图1),可在粪便中见到新鲜血液或黑粪症(图2).     

Necrotic enteritis in turkeys.

Three flocks of turkey hens (16,000 each) between 7 and 12 weeks of age experienced outbreaks of necrotic enteritis. Necropsy revealed a dilated duodenum and jejunum with mucosal surfaces covered with a diphtheritic membrane. Intestinal scrapings showed very few oocysts of Eimeria sp. Histopathological findings were compatible with necrotic enteritis but with deeper, more severe lesions than in broiler chickens. Clostridium perfringens was isolated by anaerobic culture from the intestinal contents. Mortality returned to normal after ampicillin or tetracycline was added to the drinking water.     

Hemorrhagic enteritis virus inclusions in turkey renal tubular epithelium.

Commercial turkeys from four Iowa flocks, two Illinois flocks, and three California flocks were submitted to state diagnostic laboratories because of a variety of health problems. The turkeys ranged in age from 5 to 12 weeks, included both hens and toms, and were owned by five different companies. Some flocks had previously been immunized with live hemorrhagic enteritis vaccine, and other flocks were unvaccinated. In all accessions, basophilic intranuclear inclusion bodies were observed in renal tubular epithelium by light microscopy. Transmission electron microscopy showed that the inclusions consisted of densely packed virus particles. The virions were identified as adenoviruses based upon the icosahedral morphology and average particle diameters of 72 nm. Avidin-biotin immunoperoxidase staining of formalin-fixed, paraffin-embedded kidneys was used to identify this adenovirus as hemorrhagic enteritis virus.     

Field outbreaks of colibacillosis of turkeys associated with hemorrhagic enteritis virus

In a study of field material and a survey conducted by the authors, typical signs of colibacillosis of 6-to-12-week-old poults included sudden onset, listlessness, rales, and high mortality. Signs persisted for about 2 weeks and were often followed by a low incidence of lameness caused by Escherichia coli. Gross lesions included enlarged and congested spleens and livers, and dilated discolored black or purple duodenal loops. Microscopic lesions included splenic and hepatic congestion. In some birds (freshly killed and fixed immediately), the epithelium at the tips of the duodenal villi was sloughing, but in other birds the villi were intact and normal in appearance. Splenic enlargement, the presence of intranuclear splenic inclusions similar to those found in hemorrhagic enteritis (HE), and the isolation of HE virus from some of the field spleens all indicated that inapparent HE infection often occurs at approximately the same time as this type of colibacillosis. It is therefore believed that HE infection often exacerbates colibacillosis of older poults.     

Colibacillosis of turkeys exacerbated by hemorrhagic enteritis virus. Laboratory studies

Lesions typical of colibacillosis disease were reproduced in laboratory experiments. Mortality resulting from experimentally produced colibacillosis was significantly increased when Escherichia coli O1:K1 was presented to poults that had been orally inoculated with hemorrhagic enteritis virus (HEV) 1 week earlier. These and previous data suggest that HEV infection can exacerbate colibacillosis of older poults. HEV infection apparently damages the poults' defense system enough to account for the observed increase in susceptibility to E. coli.     

In vitro evaluation of B-lymphocyte function in turkeys infected with hemorrhagic enteritis virus

Studies were conducted on B-lymphocyte function in turkeys infected with hemorrhagic enteritis (HE) virus. Hemolytic plaque-forming technique was used to detect antibody-forming cells in turkeys. The plaque-forming cell responses in HE virus-infected and noninfected controls were compared. Results of this study indicated a decreased capability of HE virus-infected turkeys to produce antibodies to sheep RBC. The greatest inhibition of antibody-forming cell production was seen in the turkeys 19 days after exposure to the virus. However, after this period, the turkeys gradually recovered their immunocompetence to sheep RBC.     

Reduced efficacy of hemorrhagic enteritis virus vaccine in turkeys exposed to avian pneumovirus

Avian pneumovirus (APV) is an immunosuppressive respiratory pathogen of turkeys. We examined the effect of APV infection on the vaccine efficacy of hemorrhagic enteritis virus (HEV) vaccines. APV was inoculated in 2-wk-old turkeys. Two or four days later, an attenuated HEV vaccine (HEVp30) or marble spleen disease virus (MSDV) vaccine were administered. Virulent HEV challenge was given 19 days after HEV vaccination. APV exposure compromised the ability of HEVp30 and MSDV to protect turkeys against virulent HEV. The protective index values were as follows: MSDV (100%) versus APV + MSDV (0%) (P < 0.05); HEVp30 (60%) versus APV + HEVp30 (30%) (P < 0.05) (Experiment I) and HEVp30 (56%) versus APV + HEVp30 (20%) (P < 0.05) (Experiment II). These data indicated that APV reduced the efficacy of HEV vaccines in turkeys.