1979 Onderstepoort Journal of Veterinary Research, Volume 46, 1979

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CONTENTS

*Volume 46: Number 1*

Composition and evaluation of the efficacy of a Staphylococcus aureus vaccine	Cameron, CM, Fuls, WJP & Botha, WF	1

Lymph node pathology in Trypanosoma brucei-infected sheep	Barrowman, PR & Roos, JA	9

Aerospora of an Eragrostis curvula pasture in South Africa	Van der Merwe, WJJ, Eicker, A, Marasas, WFO & Kellerman, TS	19

Parasites of domestic and wild animals in South Africa. XII. Artificial transmission of nematodes from blesbok and impala to sheep, goats and cattle	Horak, IG	27

Parasites of domestic and wild animals in South Africa. XIII. The seasonal incidence of adult ticks (Acarina : Ixodidae) on cattle in the Northern Transvaal	Horak, IG, De Villers, IL & Londt, JGH	31

An electron microscopic study of intra-erythrocytic stages of Babesia bovis in the brain capillaries of infected splenectomized calves	Potgieter, FT & Els, HJ	41

The experimental transmission of Parafilaria bovicola to cattle in South Africa using Musca species (subgenus Eumusca) as intermediate hosts	Nevill, EM	51

Research communications:

A bioassay method for the pheromone(s) of the bont tick Amblyomma hebraeum Koch	Brill, JG & Solomon, KR	59

The serological relationship of herpesvirus ovis to other herpesviruses and its possible involvement in the aetiology of jaagsiekte	Verwoerd, DW, Meyer-Scharrer, E, De Villiers, E-M & Broekman, J	61


*Volume 46: Number 2*

The isolation and cultivation of calf rotavirus in the Republic of South Africa	Theodoridis, A, Els, HJ & Prozesky, L	65

Trout mortalities as a result of Streptococcus infection	Boomker, J, Imes, GD & Cameron, CM	71

Gastro-intestinal helminths of domestic dogs in the Republic of South Africa	Verster, AJM	79

Cooperia connochaeti sp. nov. (Nematoda, Trichostrongylidae) from the blue wildebeest, Connochaetes taurinus (Burchell, 1823)	Boomker, JDF, Alves, R & Horak, IG	83

Genetic and physiological characterization of temperature-sensitive mutants of bluetongue virus	Shipham, SO & De la Rey, M	87

The nucleic acid and proteins of epizootic haemorrhagic disease virus	Huismans, H, Bremer, CW & Barber, TL	95

Micromorphology of the skin (epidermis, dermis, subcutis) of the dog	Schwarz, R, Le Roux, JMW, Schaller, R & Neurand, K	105

Factors affecting the bluetongue virus neutralizing antibody response and the reaction between virus and antibody	Van der Walt, NT	111

The effect of temperature on the frons width in males of Stomoxys calcitrans Linnaeus (Diptera : muscidae)	Sutherland, B	117


*Volume 46: Number 3*

Isolation and characterization of antibodies to Clostridium perfringens epsilon toxin from hyperimmune horse serum	Worthington, RW & Mulders, MSG	121

Subcutaneous and pulmonary emphysema as complications of bovine ephemeral fever	Theodoridis, A & Coetzer, JAW	125

Actinobacillus seminis infection in sheep in the Republic of South Africa. I. Identification of the problem	Van Tonder, EM	129

Actinobacillus seminis infection in sheep in the Republic of South Africa. II. Incidence and geographical distribution	Van Tonder, EM	135

Actinobacillus seminis infection in sheep in the Republic of South Africa. III. Growth and cultural characteristics of A. seminis	Van Tonder, EM	141

African Swine Fever : pathogenicity and immunogenicity of two non-haemadsorbing viruses	Thomson, GR	149

The role played by wildlife in the epizootiology of rabies in South Africa and South West Africa	Barnard, BJH	155

Wesselsbron disease : a cause of congenital porencephaly and cerebellar hypoplasia in calves	Coetzer, JAW, Theodoridis, A, Herr, S & Kritzinger, L	165

The use of frequency diagrams in the survey of resistance to pesticides in ticks in Southern Africa	Solomon, KR, Baker, MK, Heyne, H & Van Kleef, J	171


*Volume 46: Number 4*

Descriptions of the adults and pupa of Culicoides hildae n. sp. from the Republic of South Africa (Diptera : Ceratopogonidae)	Cornet, M & Nevill, EM	179

Production and application of a live Salmonella gallinarum vaccine	Cameron, CM & Buys, SB	185

Viruses isolated from Culicoides midges in South Africa during unsuccessful attempts to isolate bovine ephemeral fever virus	Theodoridis, A, Nevill, EM, Els, HJ & Boshoff, ST	191

Studies on Haemonchus contortus. II. The effect of abomasal nematodes on subsequent challenge with H. contortus	Reinecke, RK, Snyman, HM & Seaman, H	199

Further characterization of the t-s mutant F207 of bluetongue virus	Shipham, SO	207

The immune response of horses to tetanus toxoid	Jansen, BC & Knoetze, PC	211

The haemocytology and histology of the haemopoietic organs of South African fresh water fish. I. The haemopoietic organs of Clarias gariepinus and Sarotherodon mossambicus	Boomker, JDF	217

Some effects of temperature on the adults, eggs and pupae of Stomoxys calcitrans Linnaeus (Diptera : muscidae)	Sutherland, B	223

Research communications:

Comparative efficacy of six Brucella vaccines in guinea-pigs	Cameron, CM	229

Scanning electron microscopy aided observations on and therapy of teat canal infections	Du Preez, JH	231

Author index		235

Subject index		239

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Now showing 1 - 20 of 39

Cooperia connochaeti sp. nov. (Nematoda, Trichostrongylidae) from the blue wildebeest, Connochaetes taurinus (Burchell, 1823)
(Published by The Government Printer, Pretoria, 1979) Boomker, Jacob Diederik Frederik; Alves, Regina; Horak, Ivan Gerard; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
A new species of nematode, Cooperia connochaeti, was collected from cross-bred blue and black wildebeest at Krugersdorp (Transvaal), blue wildebeest Connochaetes taurinus (Burchell, 1823) from the Kruger National Park (Transvaal) and Lake Xhau (Botswana), as well as from impala Aepyceros melampus (Lichtenstein, 1812) at Malelane (Transvaal) and Pafuri (Kruger National Park). These nematodes are smaller than Cooperia pectinata Ransom, 1907, and their spicules, which are bifid in the distal third, are shorter (145-166 µm) than those of C. pectinata (240-280 µm). In addition, the lateral branches of the dorsal ray of C. connochaeti are directed ventrally and slightly anteriorly, while those of C. pectinata are directed posteriorly.
Gastro-intestinal helminths of domestic dogs in the Republic of South Africa
(Published by The Government Printer, Pretoria, 1979) Verster, Anna J.M.; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
Of the gastro-intestinal helminths found in 1 063 dogs from different parts of the country, Dipylidium caninum, the most prevalent cestode, occurred in 19,7% of the animals. Echinococcus granulosus was present in 10 dogs, 8 of which were from urban areas, and Taenia hydatigena in 69 dogs. Taenia multiceps was recovered from dogs only in the Cape Province and the Orange Free State. Toxocara canis was present in 81 of the necropsies carried out on 253 dogs from the Pretoria municipal area, while Ancylostoma spp. were present in 175 dogs. In the Pretoria area Ancylostoma caninum (11,9%) was more prevalent than Ancylostoma braziliense (6,2%).
Trout mortalities as a result of Streptococcus infection
(Published by The Government Printer, Pretoria, 1979) Boomker, Jacob Diederik Frederik; Imes, G.D.; Cameron, Colin McKenzie; Naude, T.W.; Schoonbee, H.J.; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
Excessive mortalities were experienced in the bigger rainbow trout (Salmo gairdneri) at an efficiently managed trout farm. All tests for known toxins in the feed and water proved to be negative. A faecal Streptococcus which belongs to the Lancefield group D but which could not be identified as belonging to any of the recognized species within this group, was isolated from the spleens, livers and kidneys of affected fish. Pathogenicity studies with this organism proved it to be highly fatal to trout but not to Mozambique bream (Sarotherodon mossambicus), banded bream (Tilapia sparrmanii), carp (Cyprinus carpio) or largemouth bass (Micropterus salmoides). The isolation and biochemical characteristics of the organism are described. The symptoms, gross- and histopathology of this disease are described and discussed. The disease resembles a haemorrhagic septicaemia and appears to be associated with intensification and conditions of stress.
The isolation and cultivation of calf rotavirus in the Republic of South Africa
(Published by The Government Printer, Pretoria, 1979) Theodoridis, A.; Els, H.J.; Prozesky, Leon.; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
Calf rotavirus was cultivated and propagated in tissue culture from faeces of 3-week-old calves suffering from severe diarrhoea. Criteria for viral involvement were: production of cytopathic effects in primary foetal calf kidney cells, specific fluorescence, and identification of the agent by means of electron microscopy. In a limited serological survey the majority of the cows on an infested farm were found to possess neutralizing antibodies to the local rotavirus strain.
Subject index
(Published by The Government Printer, Pretoria, 1979) Anonymous; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
The serological relationship of herpesvirus ovis to other herpesviruses and its possible involvement in the aetiology of jaagsiekte
(Published by The Government Printer, Pretoria, 1979) Verwoerd, Daniel Wynand; Meyer-Scharrer, Elizabeth; De Villiers, Ethel-Michele; Broekman, J.; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
Cross-neutralization studies showed that 3 different isolates of herpesvirus ovis from cell cultures derived from the lungs of sheep suffering from jaagsiekte were not only identical but were also related to a similar isolate made in Scotland. No relationship, however, could be established between herpesvirus ovis and common bovine or equine herpesviruses. Antibodies to herpesvirus ovis were present in roughly 70% of all animals tested and no evidence was obtained for the involvement of the virus in the aetiology of jaagsiekte. On the other hand, the absence of antibodies in sheep sera from Iceland as well as the other data obtained in this study did not exclude involvement of the virus in jaagsiekte.
Author index
(Pretoria : Government Printer, 1979) Anonymous; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
Scanning electron microscopy aided observations on and therapy of teat canal infections
(Published by The Government Printer, Pretoria, 1979) Du Preez, J.H.; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
An examination of teat canal swabs established that 51 teat canals out of 68 quarters of machine milked cows were colonized by Staphylococcus aureus. Only 31 of these quarters yielded milk from which S. aureus could be cultured, and 6 out of the 31 produced milk containing somatic cell counts in excess of 500 000/mℓ. No inhibitory substances could be detected in milk samples 12h after 10 mg of sodium cloxacillin had been deposited in the teat canal on 1-4 successive occasions. Teat canal swabs and milk sample cultures of the same quarters became and remained bacteriologically negative for at least a week after the last treatment. Six quarters, which according to the International Dairy Federation criteria were suffering from subclinical mastitis, became negative after local teat canal therapy. Scanning electron micrographs of one infected teat canal revealed the presence of cocci in depressions and crevices on the epithelial surface, suggesting that such cocci are not always flushed out into milk samples. Teat canal therapy should make a marked contribution to the control of bovine mastitis.
Comparative efficacy of six Brucella vaccines in guinea-pigs
(Published by The Government Printer, Pretoria, 1979) Cameron, Colin McKenzie; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
Immunity assays in guinea-pigs based on spleen mass: body mass ratios showed that live vaccines were markedly more effective than inactivated oil adjuvant vaccines in providing protection against challenge with 5 000 virulent organisms.
Some effects of temperature on the adults, eggs and pupae of Stomoxys calcitrans Linnaeus (Diptera : Muscidae)
(Published by The Government Printer, Pretoria, 1979) Sutherland, B.; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
Adults could only live and reproduce to their full capacity at temperatures between 20°C and 30°C. At 15°C the females laid no eggs, the adult life span was relatively short and the reproductive capacity of females kept at 35°C was low. The thermal histories of the flies had no apparent effect on their later reactions to temperature in any of the parameters tested. The viability rates of S. calcitrans eggs exposed to temperatures between 10°C and 40°C exceeded 84%, but 45°C was lethal. The optimum temperatures for incubation of the eggs was 30°C. Pupae of S. calcitrans seemed to tolerate temperatures between 20°C and 30°C, but their mortalities increased markedly outside this temperature range. Tests showed that pupal mortalities increased linearly with increasing periods of exposure to a temperature of 15°C.
The haemocytology and histology of the haemopoietic organs of South African fresh water fish. I. The haemopoietic organs of Clarias gariepinus and Sarotherodon mossambicus
(Published by The Government Printer, Pretoria, 1979) Boomker, Jacob Diederik Frederik; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
The haemopoietic organs of the catfish, Clarias gariepinus, and the Mozambique bream, Sarotherodon mossambicus, were studied. In both species the primary haemopoietic organs are the pronephros, the mesonephros and the spleen. The peritoneum and, particularly in catfish, the momentum are of secondary importance in haemopoiesis.
A bioassay method for the pheromone(s) of the bont tick Amblyomma hebraeum Koch
(Published by The Government Printer, Pretoria, 1979) Brill, J.H.; Solomon, K.R.; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
A bioassay was developed which enabled the detection of the pheromones of the boot tick (Amblyomma hebraeum Koch) within 2 hours with a reproducibility of 82 ± 13%. Dried, solvent extracted ticks were glued onto the shaved backs of rabbits. Those ticks to which pheromone extract was subsequently applied strongly attracted females of the same species. In a 2-way choice test a cork disc impregnated with pheromone extract was even more attractive to female ticks than a treated dried tick.
Wesselsbron disease : a cause of congenital porencephaly and cerebellar hypoplasia in calves
(Published by The Government Printer, Pretoria, 1979) Coetzer, Jacobus A.W.; Theodoridis, A.; Herr, S.; Kritzinger, L.J.; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
Fifteen pregnant cows were inoculated subcutaneously and intravenously between 101-147 days of gestation with the wild-type Wesselsbron disease virus. In addition, 2 foetuses were injected directly through the uterine wall after surgical exposure of the pregnant horn. The clinical symptoms, viraemia and serology in the cows are reported, as also the gross- and histopathology and the virological and serological results of the calves and foetuses. Abortion was not an important manifestation of experimental Wesselsbron disease in cows, as it occurred in 3 animals only. Apart from a short temperature reaction in some cows no other clinical symptoms were recorded. A viraemia was not always present in these cows and, when detected, was of low magnitude and short duration. One cow, in which the foetus was inoculated at 115 days of gestation, aborted at 231 days. The foetus showed marked porencephaly and cerebellar hypoplasia.
The immune response of horses to tetanus toxoid
(Published by The Government Printer, Pretoria, 1979) Jansen, B.C.; Knoetze, P.C.; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
An intramuscular injection of 8-16 Lf tetanus toxoid in water-in-oil emulsion protected adult horses against tetanus for at least 128 weeks. A booster dose of 8 Lf toxoid in aqueous solution protected them for a further period of at least 3 years. Colostral immunity protected foals for at least 10 weeks. An intramuscular injection of 8 Lf toxoid in water-in-oil emulsion given to foals from immune dams when they were 10-18 weeks old did not elicit any antibody response. They did respond, however, to a booster injection of 8 Lf toxoid in aqueous solution given 12 weeks after the first dose. New-born foals were shown to be inherently unable to respond to an injection of tetanus toxoid.
The role played by wildlife in the epizootiology of rabies in South Africa and South-West Africa
(Published by The Government Printer, Pretoria, 1979) Barnard, B.J.H.; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
The role played by wildlife in the perpetuation of rabies is discussed in the light of information obtained during a routine examination of specimens at the Veterinary Research Institute, Onderstepoort, during the 10-year period, 1967-1976. In the course of the investigation, 9 additional hosts of rabies were confirmed and 4 rabies areas identified. The chief disseminators in 2 of these areas were found to be the dog (Canis familiaris) and the black-backed jackal (C. mesomelas); in the third area, the yellow mongoose (Cynictis penicillata), and in the fourth Genetta and Felis spp., including the domestic cat (Felis catis). It was noted that the domestic cat is of less importance in those areas where dogs and jackals are the chief disseminators.
The experimental transmission of Parafilaria bovicola to cattle in South Africa using Musca species (subgenus Eumusca) as intermediate hosts
(Published by The Government Printer, Pretoria, 1979) Nevill, E.M.; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
In controlled experiments in an insect-free stable, cattle became infected with Parafilaria bovicola when Musca lusoria, infected with the larvae of this worm, were allowed to feed on a fresh skin incision, and when infective larvae were placed on fresh skin incisions, injected subcutaneously or into the jugular vein, or instilled into the eyes. The sites of blood spots caused by ovipositing P. bovicola females and the sites of carcass lesions were seldom close to the site of infection, an indication that the worms had migrated. The prepatent period of P. bovicola in 4 cattle which developed blood spots ranged from 242-319 days. Neither of the infected cattle that were kept continuously in a shady stable showed blood spots, but 4 out of 7 infected cattle which spent some time in the sun bled. However, carcass lesions on shaded cattle were similar in appearance to those on cattle kept outdoors. Infective larvae were stimulated to escape from the mouth-parts of infected M. lusoria and Musca xanthomelas s.s. when these were fed citrated ox blood warmed to 38-40 °C. No escape took place when the flies were fed warmed saline or warmed 15% sucrose solution.
Further characterization of the t-s mutant F207 of bluetongue virus
(Published by The Government Printer, Pretoria, 1979) Shipham, S.O.; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
Temperature-shift experiments verified that the t-s lesion of BTV mutant F207 is expressed late in the replication-cycle, that is, at a stage when all virus components have already been synthesized. All viral polypeptides were indeed found in the soluble but not in the particulate fraction of cytoplasmic extracts from infected cultures grown at the non-permissive temperature. This suggests that the t-s lesion could be a defect in one or both of the polypeptides P2 and P5, which are respectively reduced in amount and absent from the latter fraction. Alternatively, the lesion could be an inability of the core particle to bind these 2 outer capsid polypeptides.
African swine fever : pathogenicity and immunogenicity of two non-haemadsorbing viruses
(Published by The Government Printer, Pretoria, 1979) Thomson, G.R. (Gavin); Gainaru, M.D.; Van Dellen, A.F.; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
The virulence of 2 non-haemadsorbing African swine fever virus isolates were compared with 2 haemadsorbing viruses. While 3 of these isolates usually produced acute death in pigs, 1 non-haemadsorbing virus caused either a fatal infection with an extended course, or few or no obvious signs of infection. Pigs that survived infection with the latter virus were resistant to the lethal effects of the other 3 strains as well as to a pool of 7 isolates made from Ornithodorus porcinus porcinus (sensu Walton, 1964) and warthog obtained in the Northern Transvaal.
An electron microscopic study of intra-erythrocytic stages of Babesia bovis in the brain capillaries of infected splenectomized calves
(Published by The Government Printer, Pretoria, 1979) Potgieter, F.T.; Els, H.J.; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M. C.; Steyn, P.J.J.
Splenectomized vaccine donor calves undergoing primary reactions to Babesia bovis infections may develop cerebral babesiosis which leads to death if not treated in time. A brain biopsy was performed on an artificially-infected animal showing nervous symptoms and the tissue was immediately processed for electron microscopic examination. Virtually every erythrocyte in the brain capillaries sectioned was infected with B. bovis. Intra-erythrocytic merozoites, trophozoites and dividing trophozoites were identified. Important features of the piriform merozoites included a reduced apical complex consisting of the anterior polar ring, microtubules, rhoptries and micronemes. Unidentified membrane-bound bodies, mostly spherical in shape, were observed anterior to the nucleus. The trophozoites showed very little structural differentiation and no food vacuoles or micropores could be detected. Each trophozoite produced 2 identical merozoites and the parent cell became totally incorporated in the daughter merozoites in the multiplication process. Projections were seen radiating from the surface of infected erythrocytes which appeared to adhere to other surfaces on contact. This probably resulted in the sludging of infected erythrocytes in the capillaries. The latter observations coincide with those described for Babesia argentina.
Actinobacillus seminis infection in sheep in the Republic of South Africa. III. Growth and cultural characteristics of A. seminis
(Published by The Government Printer, Pretoria, 1979) Van Tonder, E.M.; Bigalke, R.D.; Morren, A.J.; Verster, Anna J.M.; Verwoerd, Daniel Wynand; Walker, Jane B.; Cameron, Colin McKenzie; Gilchrist, Frances M.C.; Steyn, P.J.J.
Bacteriological tests were done on a large number of different strains of Actinobacillus seminis and also, repeatedly, on the same culture or on different cultures taken periodically from the same donor animal. These tests were also applied to strains of A . seminis representing different serological types, which in turn were compared with strains of Brucella ovis. The tests as applied proved that A. seminis strains have defined, morphological, staining, cultural and biochemical properties, although they can generally be regarded as biochemically inactive. Growth was greatly enhanced on media enriched with blood or serum and also more luxuriant when incubated in a carboxophilic atmosphere. Nitrate reduction was found to be a variable characteristic, as it was more often negative, while weakly positive and negative reactions for hydrogen sulphide production were encountered with equal frequency. On the basis of their bacteriological properties, the strains representing the different serological types can be divided into 2 groups. Strains belonging to the first of these groups conform to the earlier description of A. seminis by Baynes & Simmons (1960) and are usually catalase positive and oxidase negative, while those in the second group more closely resemble Histophilus ovis described by Roberts (1956), and produce variable reactions on the catalase and oxidase tests. Although growth did occur aerobically and was more luxuriant in a carboxophilic atmosphere in all strains, it was always much slower for strains resembling H. ovis. Similarly, the growth produced by these strains was poorer and more irregular on ordinary nutrient media and, although greatly enhanced and more regular in all strains on enriched media, it was again much slower for these strains. In all stages of development, the colonies of strains similar to H. ovis were always slower and more transparent in appearance, and tended to remain low convex and undifferentiated. Packed organisms of these strains were light yellow (lemon) in colour in contrast to strains resembling A. seminis, which had a greyish-white appearance. A. seminis and B. ovis can clearly be distinguished on their morphology, Stamp staining reaction on both semen and culture smears, colonial morphology, the delayed colony development of B. ovis and sensitivity to dyes and antibiotics.

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