Immunohistochemical detection of rinderpest virus: effects of autolysis and period of fixation

Time-Dependent Changes in Post-Mortem Testis Histopathology in the Rat

To clarify the contribution of spontaneous or autolytic post-mortem changes to testis histopathology, the testes of adult rats were examined after animals were left at room temperature for 12, 24, 36, and 48 hours postmortem (n = 2 for all time points except 0 hours postmortem, where n = 3). A progressive decrease in testis weight and seminiferous tubule diameter was observed, as well as detachment of the seminiferous epithelium from the basement membrane. As early as 12 hours postmortem, there was observable clumping and margination of chromatin in Leydig cells, Sertoli cells, spermatogonia, spermatocytes, and step 7–10 spermatids; extensive disintegration of Sertoli cells and residual bodies by 24 hours postmortem; and TUNEL positivity of Leydig cells (by 36 hours postmortem) and step 19 spermatids (at 48 hours postmortem). These findings will aid in ensuring proficient histopathological analysis of testes in toxicity studies.

Epidemiological assessment of rinderpest surveillance and control in Uganda between 1990 and 1998

Based on passive and active data, we report on an epidemiological assessment of surveillance and control of rinderpest (RP) in Uganda between 1990 and 1998. Active data were collected by administration of questionnaires to animal health personnel and their auxiliaries and to stockowners in six selected districts of eastern and northeastern Uganda. Passive data were extracted from vaccination and seromonitoring reports, and from field and laboratory reports. RP events were classified as "confirmed outbreaks", "suspected outbreaks" and "rumours". The classification of 56% of the RP events as "suspected outbreaks" indicates the difficulty in investigating disease outbreaks in Uganda. Although vaccination coverage and seroprevalence were <85% (the recommended target), they nevertheless corresponded well-reflecting effective vaccination. However, because of the low seroprevalence, a sizable population of cattle in Uganda remained at risk of RP. The agreement between the local and national disease reporting systems was low-to-moderate (kappa=0.39); this indicates inefficiency in disease reporting. Risk factors for RP outbreaks were cattle raids and communal grazing. Based on overlaid thematic maps of seroprevalence, vaccination coverage and RP events, close spatial and temporal associations were observed between cattle raids, transhumance and outbreaks and rumours. The high-risk areas were in the eastern and northeastern parts of the country. The results of this study support a phase approach of following the OIE pathway.

Seroepidemiology of rinderpest in bovids in Sri Lanka using the enzyme linked immunosorbent assay (ELISA) technique

Approximately 0.2% (n = 4397) of the bovids (cattle and buffalo) in Sri Lanka were sampled, from June 1992 using a multi-stage sampling procedure. Serum antibodies for the rinderpest virus were detected using the competitive enzyme-linked immunosorbent assay. The age, the agroclimatic zone, the management system practiced in the farms, and the vaccination history of the sampled bovids were studied as potential risk factors for being seropositive. The prevalence of rinderpest antibodies in non-vaccinated bovids was 3.5% (n = 4101). The prevalence was higher in the dry zone (9%; where the outbreak emerged in 1987), compared to bovids in the other zones (1%). Seropositive bovids over three years of age were approximately at fourfold higher chances of being seropositive compared to those that were < or = 3 years old. The higher prevalence in older animals is probably due to exposure to the virus during the 1987 epidemic. Bovids from the dry zone (annual rainfall 20 to 35 inches) were at higher odds of being seropositive even after controlling for the possible effects of age, agroclimatic zone, management system and vaccination. The fact that 62% of bovids from the dry zone in this study were reared under extensive management system (free grazing) which allow unrestricted contact between animals, may be the reason for the above finding. A relatively poor response to vaccination observed in vaccinated bovids (seroprevalence = 12%; n = 296) could be attributed to difficulties in maintaining the vaccine at recommended temperatures in the field. This is the first island-wide study on seroprevalence of rinderpest in Sri Lanka.

Detection of peste des petits ruminants virus antigen in conjunctival smears of goats by indirect immunofluorescence

Peste des petits ruminants virus (PPRV) antigen was detected in conjunctival epithelial cells obtained from goats in the early or late stage of the disease by the use of a specific monoclonal antibody (mAb) to PPRV in an immunofluorescent antibody test (IFAT). The affected goats were sampled during an outbreak of peste des petits ruminants in Eritrea. Syncytia were also observed in some smears, consistent with a morbillivirus infection, but the IFAT was more sensitive than staining for syncytia in the detection of viral antigen, the two tests giving 63 per cent and 40 per cent of animals, respectively, with positive tests. Positive immunofluorescence was observed in samples from goats in the early and late stages of the disease, but was not observed with a specific rinderpest mAb or with conjunctival smears from uninfected animals. It is concluded that preparation of conjunctival smears for staining for syncytia is a simple procedure which can be applied in the field, and by use of a specific mAb PPRV infection can be rapidly confirmed and differentiated from rinderpest.

Comparison of immunohistochemistry, electron microscopy, and direct fluorescent antibody test for the detection of bovine coronavirus

Bovine coronavirus (BCV) is 1 of the major causes of calf diarrhea and has also been implicated in respiratory infections of young calves and winter dysentery of adult cattle. Currently, transmission electron microscopy (TEM), direct fluorescent antibody (DFA), and enzyme-linked immunosorbent assay (ELISA) techniques are considered standard methods for the diagnosis of BCV infection. However, these techniques are not useful if fresh tissues and intestinal contents are not available for examination. The detection of viral antigens in formalin-fixed, paraffin-embedded tissues using immunohistochemistry (IHC) is a suitable alternative. In the present study, 166 tissue specimens were tested by IHC for the presence of BCV. These tissues were from animals whose feces were positive for rotavirus and/or coronavirus by TEM. Some of these samples were also tested by DFA. Thus, TEM, DFA, and IHC were compared for the detection of BCV. There was 56% agreement among the 3 methods (overall kappa = 0.368). When IHC was compared with TEM, 78% agreement was observed (kappa = 0.475). Similarly, IHC and DFA had 64% agreement (kappa = 0.277). These kappa values indicate a moderate degree of agreement between IHC and TEM; agreement between IHC and DFA was fair. The results of this study indicate that IHC may be a suitable adjunct for the detection of BCV because of its simplicity, ease of use, and relatively close correlation with TEM results.

A review of three pathology-based techniques for retrospective diagnosis of rinderpest, with comparison to virus isolation

Base of tongue, eyelid, and retropharyngeal lymph node were collected from three animals experimentally infected with rinderpest and utilised in a study comparing virus isolation with histopathology, immunohistochemistry, and in situ hybridisation to determine the usefulness of the latter three techniques as retrospective diagnostic aids for this disease. Virus isolation was positive for all nine samples. Histopathology was suggestive in all the tissues and definitive in some. Immunohistochemistry and in situ hybridisation highlighted the presence of rinderpest antigen of rinderpest nucleic acid in all of the sections. However, in situ hybridisation was more specific than immunohistochemistry.