Most buffaloes and cattle die six to twelve days after the onset of illness and, typically, the fetid and soiled carcass shows evidence of dehydration and emaciation (Maurer et al., 1956). The eyes are sunken, with the tear tracts scalded by a profuse mucopurulent discharge. The conjunctivas are congested and oedematous. Corneal ulceration occurs occasionally with rare instances of bilateral corneal opacity. The external nares and muzzle are encrusted with mucopurulent discharge. The hindquarters and flanks are soiled with the fetid fluid faeces. In contrast, the carcasses of buffaloes and cattle that die early in the course of the disease, before the onset of profuse diarrhoea, are often in good condition, unsoiled and free of mucopurulent crusts and discharges.
The spectacular changes observed post mortem involve the alimentary tract. At death, the characteristic erosions of the oral mucosa have usually coalesced, causing extensive desquamation of all surfaces of the mouth. The edges of the desquamated areas, like those of individual erosions, are sharply demarcated from the surrounding healthy epithelium. The desquamation often extends into the pharynx and sometimes into the upper portion of the oesophagus.
Readily visible lesions are rare in the fore stomach; if present, they are sited on the pillars of the rumen and on the surfaces of the omasal leaves. If affected, the abomasal folds are congested, oedematous and have linear erosions along the margin. The pyloric region of the abomasum is nearly always affected with necrotic patches of epithelium that slough to form bleeding ulcers, some of which contain black clots of blood. The underlying lamina propria is thickened by oedema and streaked by congestion and haemorrhage.
Lesions of the epithelium of the small intestine are similar but much less intense. They are usually restricted to the initial portion of the duodenum and the terminal part of the ileum. In contrast, Peyer's patches, like other gut-associated lymphoid tissues, are severely affected. They are swollen, black from haemorrhage and friable from necrosis.
Striking changes are observed in the large intestine. The chief sites of the lesions are the ileocaecal valve, the caecal tonsil and the crests of the folds of the caecal, colonic and rectal mucosae.
The superficial impression is that of numerous stripes of haemorrhage extending from the blind sac of the caecum to the anus, the so-called zebra stripes. In fresh carcasses of animals that die early in the course of the disease the stripes are bright red, but in the carcasses of animals that die later and in decomposed carcasses the stripes are greenish-black. The stripes are neither haemorrhages nor petechiae but greatly distended capillaries packed with erythrocytes in the lamina propria. In addition, the severely eroded mucosa oozes blood into the lumen of the gut, which fills with dark, partially coagulated fluid.
Liver and gall-bladder
The liver is not a target organ of the rinderpest virus and is therefore affected only secondarily. It usually appears normal. Occasionally, chronic passive congestion is evident. Latent hepatic pathogens are often activated by rinderpest, however, producing a striking hepatitis at death.
The mucosa of the gall-bladder reacts like that of the lower alimentary tract. Scattered petechiae and blotches of haemorrhage are evident with, on occasion, free bleeding into the lumen. Erosions are rare.
Marked changes also affect the upper respiratory tract where the turbinates and nasal septa are coated with a thick, tenacious mucopurulent exudate. The mucosae are congested, contain petechiae and are sometimes eroded, with lesions that extend into the larynx. Narrow longitudinal streaks of congestion and rusty red haemorrhage invariably mark the trachea. The lungs are often normal except in lingering cases when the animal dies after suffering severe respiratory distress. The lungs of such animals reveal spectacular alveolar and interlobular emphysema accompanied by congestion, haemorrhage and small patches of consolidation. The interlobular septa, in particular, are conspicuously filled with grossly visible air bubbles. The emphysema also often involves the periatal pleura.
Changes in the kidneys are limited to congestion in the medulla, especially at the corticomedullary junction. In contrast, the epithelium of the urinary bladder is usually severely desquamated, the underlying stroma being so heavily infiltrated by erythrocytes that the surface appears mottled with different shades of red. The urine, however, appears normal. The mucosae of the lower genital tract exhibit changes similar in character and sequence to those in the mouth.
The selective destruction of lymphocytes is the characteristic lesion of a rinderpest virus infection. All lymphoid organs are affected, with the severest damage occurring in the mesenteric lymph nodes and the gut-associated lymphoid tissues. The nodes are enlarged, soft and oedematous except in animals that die late in convalescence, when the nodes are shrunken, greyish and show radial streaks in the cortex.
The spleen usually appears normal. Occasionally, however, striking ecchymoses occur on the serosa, especially along the splenic borders. The gut-associated lymphoid tissues exhibit changes similar to those affecting the lymph nodes but their anatomical sites enable sloughing of the necrotic debris, creating deep craters in the intestinal wall that ooze blood.
The heart is usually grossly normal except in animals that die early in the course of the disease from cardiogenic shock. The lesions, however, are non-specific and consist of a variable degree of subendocardial haemorrhage in the left ventricle, rarely in the right ventricle, and subepicardial petechiae on the base of the heart. Petechiae occasionally occur on the apex and along the coronary grooves. The myocardium tends to be flabby.
In the past, cutaneous rinderpest eruptions were often reported and, in fact, many vernacular names in Africa and Asia for the disease mean "pox". However, skin lesions are seldom seen. The lesions allegedly emerge first as discrete macules that rapidly become papules, then vesicles and finally pustules. The exudate mats the hair into tufts. The common sites are the fine-skinned areas of the body around the anus, on the perineum, udder or scrotum and between the legs. Buffaloes are alleged to be particularly prone to rinderpest skin lesions. Microscopic and ultramicroscopic examinations reveal either Dermatophilus congolensis or a pox virus or both.
In countries where the disease is enzootic, cases of rinderpest in goats and sheep tend to be subacute and most survive. Lesions in slaughtered animals are vague and far from suggestive. Lesions in acutely ill goats and sheep that die mimic those seen in cattle but tend to be less intense. Pulmonary involvement, however, is more frequent than in cattle.
The carcass is emaciated, fetid and soiled. The eyelids are matted with mucopurulent exudate and the nostrils are encrusted and often blocked with a mucopurulent nasal discharge.
The lips are hyperaemic. Stomatitis may or may not be evident; if present, it may range from a few sharply demarcated erosions to extensive desquamation of the oral epithelium that may extend into the congested pharynx.
Obvious changes in the oesophagus and fore stomach have not been described, although it has been noted that the ingesta in the omasum are often liquid. The mucosa of the abomasum is invariably involved, although the intensity of the lesions varies enormously. Sometimes the mucosa is merely diffusely congested, at other times it is also petechiated and eroded. The pyloric portion of the abomasum is usually ulcerated and the ulcers are often coated with a tenacious grey pseudomembrane.
Severe congestion and erosion may extend throughout the length of the small and large intestines but usually the gross changes are limited to the duodenum, the terminal ileum, the caecum and upper colon. The ileocaecal valve is a prominent site of congestion and may ooze blood. Zebra stripes mark the crests of the folds of the caecal, colonic and rectal mucosae. Erosions and ulcerations are usually restricted, however, to the mucosae of the caecum and rectum.
Liver and gall-bladder
Both the liver and gall-bladder appear grossly normal. Most observers are struck by the absence of changes in the mucosa of the gall-bladder and in the character of the bile.
Secondary purulent bronchopneumonia is a conspicuous lesion and usually affects the apical and cardiac lobes of the lungs. It is attributable to activated pasteurellas. Emphysema is not common. The mucosae of the upper respiratory tract are congested, eroded and coated with a thick mucopurulent exudate. Congestion lines the upper trachea.
Congestion and erosion of the mucosa of the urogenital tract occur occasionally. The kidneys are usually normal, with any changes being considered non-specific.
Lymph nodes are conspicuous, being oedematous and soft. Congestion, in addition, has been observed in the retropharyngeal lymph nodes. Spleens are usually normal but occasionally may be swollen. Capsular blood vessels are sometimes engorged. The gut-associated lymphoid tissues are all attacked, the large Peyer's patch in the terminal ileum in particular being obviously affected. The necrosis leads to sloughing, which produces craters that ooze poorly clotting blood.
Subepicardial petechiae sometimes occur in the coronary grooves, but otherwise the heart usually appears grossly normal.
Cutaneous lesions, pock-like in character, have been described as affecting the skin without hair or wool.
Rinderpest virus kills Asian domestic pigs but not European-type domestic pigs. Fatal infections also occur in African wild pigs such as the warthog, bush pig and giant forest hog.
The carcass is in poor condition, soiled with fluid faeces and fetid (Hudson and Wongsongsarn, 1950).
The stomatitis ranges in severity from cyanosis at the back of the tongue and in the pharynx to extensive diphtheresis involving all the oral surfaces. The gastritis likewise varies from mild hyperaemia in the pyloric region to an overall, diffuse, deep congestion with necrosis, desquamation and ulceration of the epithelium. The ulcers are often covered by diphtheritic pseudomembranes. Lesions in the small intestine are usually limited to the Peyer's patches, but, on occasion, a haemorrhagic enteritis extends from the duodenum to the rectum. Lesions are usually prominent in the caecum and include congestion, ulceration and diphtheria; in pigs that die late in the disease, the necrotic ulcers in the caecum may be the sole lesions. The colonic mucosa has irregular blotches of congestion along its length.
Liver and gall-bladder
The liver is not affected. The lesions in the gallbladder, however, range from mild vascular arborescence to diffuse congestion of the mucosa.
Gross changes in the respiratory tract are common and consist of cyanosis of the larynx, haemorrhagic streaks in the upper trachea, pulmonary congestion and patches of secondary bronchopneumonia.
Opinions clash regarding the frequency of pulmonary emphysema.
The kidneys and the mucosa of the urinary bladder are both congested, but the intensity of the congestion varies.
Lymphoid organs exhibit a variety of necrotic lesions that are particularly conspicuous in the gut-associated lymphoid tissues. The spleen is usually grossly normal although it may be swollen on occasion.
The heart, at most, shows pale, dry areas in the myocardium. Subendocardial and subepicardial haemorrhages have not been described. The blood is dark but clots promptly.
Changes in the skin are common, ranging from discrete areas of congestion and cyanosis on the abdomen and legs to extensive purple blotching and subcutaneous ecchymoses. Eczematous eruptions may occur around the anus and on the perineum.