Placental pathology of the pregnant mouse inoculated with Brucella abortus strain 2308.

Fifty-five pregnant BALB/c mice received various doses of Brucella abortus virulent strain 2308 intraperitoneally on day 9 of gestation, and uteri and spleens were examined at 3, 5, 7, and 9 days post-inoculation to study the pathogenesis of infection. A dose of 10(5.7) B. abortus organisms produced a severe, necrosuppurative placentitis. Bacteria multiplied preferentially within the placenta and were identified within the rough endoplasmic reticulum of trophoblast giant cells and within the visceral yolk sac endoderm. Abortions did not occur, but infarction of the labyrinth region of severely affected placentas occasionally resulted in fetal death. The severity of infection in the spleens of nonpregnant mice receiving the same challenge dose was not significantly different from that in the spleens of challenged pregnant mice. These results suggest that the sensitivity of the pregnant mouse to placental brucellosis is not due to a generalized immunosuppression but rather may involve a combination of local suppression of the immune response and a susceptible cell population suitable for Brucella colonization and replication. Experimental murine brucellosis resembles ruminant brucellosis and provides a model to study the intracellular replication of B. abortus in trophoblasts.

Comparative behaviour of Brucella abortus strains 19 and RB51 in the pregnant mouse.

Pregnant BALB/c mice received various doses of either Brucella abortus strain 19, a smooth vaccine strain, or B abortus strain RB51, a stable rough organism, intraperitoneally on day 9 of gestation to compare the relative pathogenicity of the two attenuated strains. Nine days after inoculation, spleens and placentas were collected for bacteriological and histopathological examination. A dose of 10(7.5) and strain 19 organisms produced a severe necrosuppurative placentitis occasionally accompanied by fetal death. This dose resulted in a 10-fold higher level of splenic infection than did a dose of 10(9.5) strain RB51 organisms, which produced only mild to minimal placentitis not associated with fetal death. Strain 19 infected mice showed seroconversion in the standard tube agglutination test in contrast to the seronegative titre of strain RB51 infected mice. The results of this study corroborate previous investigations on the relative pathogenicity and the serological response of the non-pregnant mouse to strain RB51.

Transdiaphragmatic approach to thoracic duct ligation in the cat.

An approach combining ventral midline celiotomy with transdiaphragmatic thoracotomy was evaluated in eight healthy cats for ligation of the thoracic duct system. Evans Blue solution was injected into the right colic lymph node to outline the intestinal lymphatic trunk and the thoracic duct system. Three cats (group 1) had mesenteric lymphangiograms and three (group 2) had only lymph node dye injection before thoracic duct ligation. The thoracic duct system was ligated with hemostatic clips just cranial to the aortic hiatus of the diaphragm, through a left transdiaphragmatic thoracotomy. Two cats (group 3) had prethoracotomy mesenteric lymphangiograms and thoracic duct isolation without ligation. Mesenteric lymphangiography was performed immediately after the surgery. In all of the cats, an absence of contrast medium in the thoracic duct system cranial to the surgical site was interpreted as complete obstruction. Four weeks after ligation, there was complete obstruction of the thoracic duct system with alternate lymphaticovenous communications in four of the six cats with ligated thoracic duct systems. Partial obstruction of the thoracic duct system with alternate lymphaticovenous communications was present in the other two cats. Both cats without thoracic duct ligation had patent thoracic duct systems. At necropsy of the six cats with ligated thoracic ducts, there was mild focal lymphadenitis of injected lymph nodes in three cats. The wall of the aorta adjacent to the hemostatic clips was normal in all six cats. The surgical technique was simple and provided excellent exposure. Vital staining with Evans Blue helped visualize the thoracic duct system, but mesenteric lymphangiography did not. Postligation lymphangiography was not of value in identifying incomplete ligation.

Enterocolitis caused by Ehrlichia sp. in the horse (Potomac horse fever).

Potomac horse fever was reproduced in 15 ponies by transfusion of whole blood originally from two natural cases and subsequently from ponies infected by the transfusions. Incubation periods varied from 9 to 15 days. Affected ponies developed varying degrees of fever, diarrhea, anorexia, depression, and leukopenia. Eleven affected ponies were killed, three died in the acute phase of the disease, and one did not show clinical signs. The most consistent post-mortem findings were fluid contents in the cecum and large colon, and areas of hyperemia (of inconstant degree and distribution) in mucosae of both small and large intestines. Multifocal areas of necrosis occurred in mucous membranes. Ehrlichial organisms were most common in the cytoplasm of epithelial cells, macrophages, and mast cells of the large colon.

Ultrastructural study of ehrlichial organisms in the large colons of ponies infected with Potomac horse fever.

Potomac horse fever is characterized by fever, anorexia, leukopenia, profuse watery diarrhea, dehydration, and high mortality. An ultrastructural investigation was made to search for any unusual microorganisms in the digestive system, lymphatic organs, and blood cells of ponies that had developed clinical signs after transfusion with whole blood from horses naturally infected with Potomac horse fever. A consistent finding was the presence of rickettsial organisms in the wall of the intestinal tract of these ponies. The organisms were found mostly in the wall of the large colon, but fewer organisms were found in the small colon, jejunum, and cecum. The organisms were also detected in cultured blood monocytes. In the intestinal wall, many microorganisms were intracytoplasmic in deep glandular epithelial cells and mast cells. Microorganisms were also found in macrophages migrating between glandular epithelial cells in the lamina propria and submucosa. The microorganisms were round, very pleomorphic, and surrounded by a host membrane. They contained fine strands of DNA and ribosomes and were surrounded by double bileaflet membranes. Their ultrastructure was very similar to that of the genus Ehrlichia, a member of the family Rickettsiaceae. The high frequency of detection of the organism in the wall of the intestinal tract, especially in the large colon, indicates the presence of organotrophism in this organism. Infected blood monocytes may be the vehicle for transmission between organs and between animals. The characteristic severe diarrhea may be induced by the organism directly by impairing epithelial cell functions or indirectly by perturbing infected macrophages and mast cells in the intestinal wall or by both.

Observations on acute salmonellosis in four Waikato dairy herds.

Acute epidemic salmonellosis was investigated in the winter of 1978 in 4 dairy herds in the Waikato district. The outbreaks involved pregnant or recently calved cows. Calves were affected on only one farm. Salmonella bovismorbificans was isolated from the faecal, uterine and environmental samples from the herd most severely affected. In this herd 20, (20%) of the cows died; 10 calves were either born dead or died soon after birth; and 10 cows were culled as unlikely to return to production. S. typhimurium was involved in the outbreaks in the other 3 herds and from one of these farms salmonellae were isolated from the faeces of the 2 farm dogs and from a 12-month-old infant with dysentery. Salmonellae were recovered from all of the clinically ill cows and from 36% of the asymptomatic animals. Salmonellae were widespread on the properties and were isolated from 81% of soil samples; 36% of drain swabs; and from all the pairs of rubber boots worn while collecting samples.

Superphosphate poisoning of sheep: a study of natural outbreaks.

Superphosphate poisoning is typically a disease of pregnant and lactating ewes under nutritional stress. Poisoning has been observed only in the late winter and spring. Most episodes occurred when hungry sheep were forced to graze short pastures top-dressed within one week prior to the onset of clinical signs. Fine weather which is favourable for the application of fertiliser also favours the occurrence of poisoning. Clinical signs include anorexia, thirst, diarrhoea, weakness and incoordination. Death usually occurs within 48 hours of the onset of clinical signs. In some outbreaks the presenting signs are those of hypocalcaemia but response to calcium therapy is transient. Poisoning results in a toxic tubular nephritis and uraemia. No satisfactory treatment can be suggested but poisoning can be prevented by avoiding exposure of sheep to top-dressed pastures.

Leptospirosis: II. Investigation of clinical disease in dairy cattle in the Waikato district of New Zealand.

Investigations were carried out in 1975, 1976 and 1977 in 16 dairy herds where leptospiral abortions were suspected and in five other herds where clinical disease was not present. Both Leptospira interrogans serovars pomona and hardjo were isolated from cattle in herds with leptospirosis, but only pomona was recovered from those that had aborted. There was no evidence that hardjo caused clinical disease in dairy cattle in the Waikato district. It was found that 73% of the cows that aborted and 19% of other animals in the same herds had microscopic agglutination test titres to pomona of 1:2,000 or greater. By contrast, only 2% of cattle in herds without clinical evidence of leptospirosis had such titres. One cow retained a titre of 1:2,000 or greater to pomona for 7 months; titres of this order had a shorter duration in other cows. Leptospiruria occurred in 50% of cows that had aborted and in 9% of in-contact cows in the same herds. Only 0.7% of cows had leptospiruria in the herds with no clinical disease. Ten of 35 cows shedding pomona still had leptospiruria one month later. It was concluded that clinical leptospirosis should be diagnosed by testing a sample of the herd, rather than just individual cows, because of the variability and persistence of leptospiruria and serological titres in cows with and without clinical signs. Although hardjo is common in cattle in the Waikato district, it was not found to cause abortion in cattle.

Leptospirosis: I. Clinical investigation of the infection in dairy cattle in the Waikato district of New Zealand.

An investigation was made into the prevalence of leptospiral infection in cattle. An area 50 km radius was selected in a region where leptospirosis was reputedly common. Farmers volunteered 250 herds with 39 500 cows for testing and 7 500 animals were selected and sampled. Twenty-nine cows (0.4%) on 14 (5.6%) of the farms had leptospiruria at the first examination. Leptospirae were cultured from the urines of nine of these animals and all were Leptospira interrogans serovar hardjo. Serologically 12.5% of cows had titres of 1:200 or greater to hardjo and 3.5% titres of 1:200 or greater to pomona. In the Spring of 1977, there was evidence of clinical leptospirosis in calves associated with only one of the herds and no clinical leptospirosis in the 250 lactating herds, although leptospiral titres were found in 88% of them. This indicated that clinical disease was much less common than infection. We concluded that leptospirosis was of minor economic importance in dairy cattle, although it could be significant in individual herds, and a health hazard to farm workers.

Dolphins and their diseases.

Thirty-eight species of small cetaceans termed "dolphins" and "porpoises" are listed. This review is a contribution to the growing community and veterinary interest in the welfare and diseases of these animals.

The causes of whale strandings.

Strandings of cetaceans (whales and dolphins) is probably the result of a sequence of events rather than a simple cause-and-effect relationship. Strandings of solitary animals are more common than massed and generally thought to be due to severe disease. Mass strandings (three to several hundred individuals) are less common, but very spectacular. Mass strandings are considered to be due to a complex of factors in which behavioural factors are probably important, severe disease making an unimportant, or negligible contribution. There may be interaction of physical conditions (weather, tides, currents, coastline) and biological conditions (predators, feeding, disturbance of echolocation and disease) which result in stranding. One postulated reason for stranding is that it is dependent on instinctive behaviour, deeply located in subcortical areas of the brain, which provokes cetaceans to seek refuge ashore when under stress.

Data management for the International Registry of Reproductive Pathology using SNOMED coding and computerization.

The International Registry of Reproductive Pathology contains more than 19,000 case records. It is indexed with the aid of Systematized Nomenclature of Medicine (SNOMED) codes and the MUMPS-11 interactive computer language. A package of programs was developed to maintain an index file of cases in the collection and to produce for each species a printed list of case numbers for every combination of topography, morphology and etiology. The printed disease data from the computer are in English with corresponding SNOMED code numbers and relevant case numbers.