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Actinobacillus suis–like organisms (ASLOs) have been isolated from the genital, respiratory, and digestive tracts of healthy adult horses, horses with respiratory disease, and septic foals. Two foals with congenital hypothyroidism–dysmaturity syndrome from separate farms developed ASLO infection. At necropsy, both had contracted carpal flexor tendons, thyroid hyperplasia, and thrombotic and necrotizing mesenteric lymphangitis and lymphadenitis; one foal also had mandibular prognathism. Numerous ASLOs were isolated from tissues from both foals, including intestine. Biochemical testing and mass spectrometric analysis of the two Actinobacillus isolates did not allow unequivocal identification. Comparative genetic analysis was done on these and similar isolates, including phylogeny based on 16S rRNA, rpoB and recN genes, as well as RTX (repeat in toxin) toxin typing of apxIA– apxIVA and aqxA genes. One isolate was identified as Actinobacillus suis sensu stricto, based on the presence of apxIA and apxIIA but not aqxA, whereas the other isolate had aqxA but neither apxIA nor apxIIA, consistent with A equuli ssp haemolyticus. Based on genotypic analysis of the isolates included for comparison, 3 of 3 equine ASLOs and 2 of 5 A equuli isolates were reclassified as A equuli subsp haemolyticus, emphasizing the importance of toxin genotyping in accurate classification of actinobacilli.

A serological test involves detection of specific changes, induced by a pathogen, in the properties or actions of serum of an infected host. The test may detect the presence in serum of either antibodies to the pathogen (produced by the host) or antigens (i.e. the infecting agent itself and/or its components). The many serological tests which have been developed for the diagnosis of contagious bovine pleuropneumonia (CBPP) are classified into two groups on the basis of this distinction. To date, no single serological test is able to detect all stages of the disease. Thus the choice of serological test (or combination of tests) will depend on the specific aim of the investigation. Meanwhile, a sensitive, specific and simple 'pen-side' test for the diagnosis of all forms of CBPP is still lacking.

A previously described mouse monoclonal antibody (WM25), directed against the caprine pathogenic mycoplasma strain F38 (Mycoplasma capricolum subspecies capripneumoniae), was further examined for its diagnostic efficacy in serological tests against various isolates of this group and of each of the five other 'M mycoides cluster' groups (M mycoides subspecies mycoides, small colony (SC) and large colony (LC) biotypes, M mycoides subspecies capri, M capricolum subspecies capricolum and bovine group 7) and M agalactiae. The methods used were the conventional disc-growth inhibition and colony-immunofluorescence techniques. The same strains were also tested against polyclonal rabbit antisera for each mycoplasmal group. With the polyclonal antisera, many cross reactions occurred between members of the different groups. The two F38-polyclonals gave cross reactions only against various M capricolum subspecies capricolum and bovine group 7 strains, apart from one of M mycoides SC in the immunofluorescence test only. The F38 monoclonal antibody gave more specific results, in that only the F38-type strains (M capricolum subspecies capripneumoniae) and three of the four bovine group 7 strains reacted positively in growth inhibition tests; the only heterologous reaction by colony immunofluorescence was with one M capricolum subspecies capricolum strain. The F38 monoclonal antibody, WM25, may therefore be useful for the specific serological identification of caprine F38-type isolates by the disc-growth inhibition method, which will exclude M agalactiae, M capricolum subspecies capricolum and the other members of the 'M mycoides cluster' associated with goats, but not bovine group 7 (which is not found in goats), which can be excluded by colony immunofluorescence tests.

The DNA probe pCS20, which was cloned from the DNA of the Crystal Springs heartwater strain from Zimbabwe, cross-reacted with DNAs of heartwater strains from all endemic areas, including four heartwater strains from Zimbabwe, two strains from South Africa, one strain from Nigeria, and the Gardel strain from the Caribbean island of Guadeloupe. By nucleic acid hybridization, the pCS20 DNA probe detected Cowdria ruminantium DNA in all DNA preparations made from plasma samples from infected sheep before and during the febrile reaction. Synthetic oligonucleotides were prepared for amplification of specific C. ruminantium DNA sequences by the polymerase chain reaction (PCR). Amplification of two DNA products (181 and 279 bp) from pCS20 DNA and C. ruminantium genomic DNA of heartwater strains was demonstrated. In contrast, amplification of these products or any other products was not possible from genomic DNAs of Anaplasma marginale, Babesia bigemina, Trypanosoma brucei brucei, Escherichia coli, and bovine endothelial cells. The cross-reactivities of the 32P-labeled PCR products with genomic DNAs from several heartwater strains were similar to those with the pCS20 DNA probe. A nucleic acid-based test that uses hybridization assays and PCR provides a sensitive method for the detection of heartwater in both animals and ticks and has applications in epidemiological studies for the disease, which may allow for improved disease control.

Three Swainson's Blue Mountain Rainbow Lorikeets ( Trichoglossus haematodus moluccanus), ranging from 6 to 8 months of age, presented with lethargy, emaciation, and progressive neurologic signs. The first one died 24 hours after the onset of clinical signs, and the other two were euthanized 10 to 14 days after the onset of progressive neurologic disease. Clinical signs in these lorikeets included head pressing, hemiparesis, seizures, obtunded mentation, weakness, and lethargy. Two of the lorikeets had hepatomegaly, and one had splenomegaly on gross examination. Histopathology revealed disseminated microgranulomas in the liver, spleen, and brain, and lymphohistocytic perivascular encephalitis and cephalic vasculitis. Electron microscopic examination of macrophages in brain lesions revealed spherical to rod-shaped prokaryotic organisms with a trilaminar cell wall. Molecular analysis revealed a novel species of Coxiella. This is believed to be the first report of a Coxiella sp. causing disease in a lorikeet.

Administration of specific goat anti-thymocyte serum (ATS) to rabbits, prior to a primary infestation by Rhipicephalus appendiculatus larvae, blocked the acquisition of resistance significantly only in the third infestation. The larvae which fed on these rabbits had higher engorgement masses than did those feeding on untreated control rabbits. Also, a higher percentage (92%) of larval ticks fed on these animals than on the controls (88%). ATS also induced a leucopenia due to a lymphopenia in the treated rabbits. It was concluded that a T-cell-dependent component might be involved in acquired resistance to infestation by R. appendiculatus.

Parenteral administration of cyclophosphamide in rabbits made resistant to infestation by the tick Rhipicephalus appendiculatus, resulted in abrogation of the resistance phenomenon. As a result, a high percentage (83%) of the larval ticks fed to repletion. This was in contrast to the control rabbits which were expressing the phenomenon of resistance to infestation by the ticks. In the latter, only 28% of the ticks fed to repletion. Cyclophosphamide administration in rabbits induced a leucopenia and depressed antibody response to the heterologous antigen, sheep red-blood cells.

A serological test involves detection of specific changes, induced by a pathogen, in the properties or actions of serum of an infected host. The test may detect the presence in serum of either antibodies to the pathogen (produced by the host) or antigens (i.e. the infecting agent itself and/or its components). The many serological tests which have been developed for the diagnosis of contagious bovine pleuropneumonia (CBPP) are classified into two groups on the basis of this distinction. To date, no single serological test is able to detect all stages of the disease. Thus the choice of serological test (or combination of tests) will depend on the specific aim of the investigation. Meanwhile, a sensitive, specific and simple 'pen-side' test for the diagnosis of all forms of CBPP is still lacking.

This study compares the susceptibility of African buffalo (Syncerus caffer) and Boran cattle (Bos indicus) to intravenous infection with T. congolense blood stream forms. The trypanosomes multiplied in the buffaloes and the Boran and reached levels of detectable parasitaemia 4 days after infection in the Boran and 10 days after infection in the buffalo. The cattle developed severe anaemia and had to be treated 60 days after infection to save them from dying whereas the buffaloes did not develop any signs of anaemia and did not require treatment. The Boran cattle showed high levels of parasitaemia persisting throughout the experimental period with some fluctuations. The parasitaemia in the buffaloes reached a peak of 5 x 10(3)/ml, 100 fold below the maximum level in cattle, it was intermittent and by the end of the experimental period (60 days), 3 out of 4 buffaloes had eliminated the parasites from circulation. Neutralizing antibodies were detected at the time of peak parasitaemia or soon after the 1st peak parasitaemia in buffaloes whereas in the Boran cattle neutralizing antibody could not be detected until after several peaks of parasitaemia. Neutralizing antibody persisted both in the Boran and buffaloes until the end of the experimental period.

The mode of transmission of malignant catarrhal fever virus (MCFV) from wildebeest to cattle has been obscure for some time. Recent studies on the virus shedding patterns of wildebeest have revealed that MCFV occur in nasal and ocular secretions of young wildebeest in a stable, cell-free state. Such cell-free virus is not found in the secretions of MCFV infected cattle. The findings indicate that MCFV is transmitted from wildebeest to cattle as cell-free virus shed in the secretions of young wildebeest calves and may explain the non-contagious nature of the disease in cattle. The mode of transmission of sheep-associated MCF has not been determined because the causative agent of this condition has not been isolated from either carrier sheep or sick cattle.

Rabbits pretreated with cyclophosphamide for 7 days (CY+) and control rabbits (CY-), were infected with cell-associated malignant catarrhal fever virus (MCFV), and CY treatment of the CY+ group was continued to day 20 p.i. The time of onset and degree of antibody formation to bovine serum albumin was significantly suppressed in the CY+ group whilst the humoral antibody response to MCFV appeared to be delayed rather than suppressed. Although incubation periods of the disease were comparable in the CY+ and CY- groups, the disease course was much shorter in the CY- group, 100% mortality occurring within a mean of 4.5 days, as opposed to a mean of 15 days in CY+ animals. Mortalities did not occur in the CY+ group until a mean of 5.5 days following withdrawal of CY. In further experiments it was shown that pre-existing antibody to MCFV had no effect on the incubation period and course of MCF in rabbits. The results thus suggest that MCF may not be an immune complex disease.

Malignant catarrhal fever virus (MCFV) infectivity was demonstrated in macrophages/monocytes collected from MCFV-infected rabbits. Thus, in addition to lymphocytes, macrophages and monocytes are probably involved in the pathogenesis of MCFV and could account for the widespread dissemination of MCFV, the very high mortality rate and the immunosuppression observed in MCFV-infected animals.

The homologous skin sensitizing activity of serum from tick-naive cattle (Bos taurus) and from cattle resistant to the tick Rhipicephalus appendiculatus was tested by attempting to induce passive cutaneous anaphylaxis (PCA) in tick-naive calves. The serum from tick-resistant cattle induced PCA, whereas that from tick-naive cattle failed to do so. The PCA was more marked at 72 hours than at 24 hours after administration of the serum. Treatment of the serum by heat at 56 degrees C for 2 hours or by adding 0.1 M 2-mercaptoethanol to it reduced its ability to sensitize. Serum from tick-resistant cattle did not sensitize the skin of heterologous species, namely rabbits, guinea-pigs and rats.

Serum levels of the third component of complement (C3) were reduced only in the terminal stages in malignant catarrhal fever (MCF) virus-infected steers. Haemolytic complement and immunoglobulin (IgM, IgG1 and IgG2) levels were not altered. C3 and immunoglobulin deposits were also not demonstrated in the vascular lesions induced by MCFV. MCF virus infection of cattle is probably not a typical immune complex-mediated disease as previously suggested.

Infections with Trypanosoma congolense or T vivax did not significantly depress the neutralising antibody response of cattle to live rinderpest vaccine when vaccination was carried out eight or 25 days after infection.

Trypanosoma congolaise and T vivax infections in cattle were shown to have a suppressive effect on the secondary humoral immune response to M mycoides. The trypano- some infections caused an involution of the thymus. The secondary response was blphasic in nature and was unrelated to infection with trypanosomes.

A combination of dihydrostreptomycin sulphate (250 mg/ml) and penicillin G procaine (200,000 iu/ml) was used to treat contagious caprine pleuropneumonia caused by F38 strain of mycoplasma. A single dose of either 20, 30, 40 or 50 mg/kg body weight of the dihydrostreptomycin sulphate led to the recovery of the treated goats. The recovered goats did not transmit CCPP to susceptible goats housed with them for 2 months. The goats which recovered were found to be solidly immune to an in-contact challenge in which all the control goats died of CCPP. The treated and recovered goats were found not to be carriers of the organism.

A significant passive protection against contagious bovine pleuropneumonia (CBPP) was demonstrated in cattle. One group of cattle was inoculated with serum from CBPP-recovered cattle, while another group was inoculated with serum from susceptible cattle. The two groups, along with an untreated control group, were challenged with the virulent Gladysdale strain of Mycoplasma mycoides, using the in-contact method. Four out of the five cattle inoculated with serum from animals which had recovered from CBPP were protected, whereas three of five cattle inoculated with serum from susceptible animals and all the untreated animals died of CBPP.

The antigenic relationship amongst sporozoites of several Theileria parva strans isolated from different parts of East Africa was investigated. It was found that antibodies to T. parva ( Muguga ) sporozoites neutralized the infectivity of homologous sporozoites as well as those of T. parva (Uganda), T. parva lawrencei , T. parva ( Kiambu 5), T. parva ( Kabete 1) and T. parva ( Marikebuni ). The results correlated with those obtained from an in vivo challenge, in that cattle immunized against T. parva ( Muguga ) were either solidly resistant or developed only a transient parasitosis when challenged with T. parva lawrencei or T. parva (Uganda). The immunity exhibited by these animals paralleled the level of anti-sporozoite antibodies, such that animas with high titres were completely protected whereas those with low levels developed transient parasitosis. Furthermore, monoclonal antibodies made against sporozoites of T. parva ( Muguga ) were also capable of neutralizing the infectivity of sporozoites of other strains. These results indicate that the outcome of cross-challenge may depend on the level and avidity of the anti-sporozoite antibodies at the time of challenge. In addition, these findings show that there is a common protective antigenic determinant on sporozoites of all the T. parva strains investigated in this study.

Specific antisera against sera of 46 species of vertebrates were prepared. The antisera to 21 Bovidae species were raised in goats except the antiserum to goat serum which was raised in sheep. The antisera to 3 Suidae species were produced either in domestic pigs or warthogs, while antisera to most of the other vertebrate species were raised in rabbits. The antisera were used in an enzyme-linked immunosorbent assay (ELISA) to identify the source of bloodmeals ingested by teneral and non-teneral tsetse at different time intervals after feeding. The bloodmeal donors were identifiable in 100% of the teneral tsetse up to 40 h post-feeding and in 87.5% in those tested up to 74 h post-feeding. Non-teneral tsetse digested the species-distinguishing bloodmeal components faster than the tenerals. Bloodmeals could be identified in 100% non-tenerals at 20 h post-feeding but only 67.5% and 50% of the bloodmeals could be identified 40 h and 74 h post-feeding, respectively. The antisera were also able to identify mixed bloodmeals from closely related species.

Three groups of 15 goats each were immunised against contagious caprine pleuropneumonia (CCPP) using sonicated antigens of the F-38 strain of mycoplasma incorporated in incomplete Freund's adjuvant (IFA), emulsified in aluminium hydroxide and phosphate buffered saline respectively. Three months after immunisation, five goats from each group were challenged by the in-contact method. The goats immunised with the antigen incorporated in IFA were all solidly immune to the challenge whereas only two of five of the goats in the other two groups were protected. When the remaining 10 animals from each group were challenged six months after immunisation, those immunised with the antigen in IFA were still solidly immune while only two goats from each of the other two groups were protected. These results show that effective immunity against CCPP caused by the F-38 strain can be induced by vaccination with sonicated F-38 antigens emulsified in IFA.

Cattle infected with Trypanosoma congolense were intravenously immunized with Leptospira biflexa 15 days after trypanosomal infection. The primary immune response to L. biflexa was considerably reduced as compared to uninfected controls. The infected cattle mounted a secondary response when they were cured of trypanosomes by treatment with Berenil 25 days after infection and re-immunized 8 days later. The mean secondary response in these previously infected animals was lower tha, but not significantly different from that of the uninfected control animals. Serum collected 15, 20 and 25 days after infection was inhibitory to the migration of both autologous and isologous (control) peripheral blood leucocytes. The migration inhibitory activity was abolished by heating the serum at 56 degrees C for 30 minutes implying the involvement of a heat labile serum component(s). The same serum did not modify the mitogenic effect of PHA on autologous peripheral lymphocytes.

Infections with Trypanosoma congolense or T vivax did not significantly depress the neutralising antibody response of cattle to live rinderpest vaccine when vaccination was carried out eight or 25 days after infection.

A polysaccharide was extracted by warm aqueous phenol from the F-38 strain of mycoplasma which causes contagious caprine pleuropneumonia (CCPP). After acid hydrolysis, the polysaccharide was found to be composed of the neutral sugars glucose, galactose, mannose and fucose and the amino sugars galactosamine and glucosamine. All the sugars were present in approximately equal quantities. Unmodified goat erythrocytes bound the polysaccharide readily and the sensitised cells reacted with antibodies in sera from goats with experimental or natural CCPP. The unique composition of the F-38 polysaccharide and the specific reactivity of polysaccharide-sensitised red cells with antibodies from CCPP infected animals suggests that the polysaccharide should be useful for identification of F-38 organisms and diagnosis of the disease.

Passive haemagglutination and complement fixation tests were used to assess the antibody response of goats to the F-38 strain of mycoplasma. The passive haemagglutination test was found to have a positive correlation (r:0.89) with the complement fixation test in detection of antibody to strain F-38. Whereas passive haemagglutination was found more sensitive than the complement fixation test, it was less specific.

Lymphocytes from lymph nodes and spleens of malignant catarrhal fever virus (MCFV) infected rabbits were tested for MCFV infectivity in secondary calf thyroid cell monolayers. Most infectivity was demonstrated in the lymphocytes. Some infectivity was also detected in macrophages/monocytes. It was thus concluded that lymphocytes form the major target cell for the herpesvirus of malignant catarrhal fever in rabbits.

Wildebeest IgA was isolated from nasal secretions and precolostrum. It was identified by cross-reaction with anti-human and anti-bovine IgA sera. Nasal secretions collected from wildebeest calves over 3 months old had malignant catarrhal fever virus neutralizing antibody activity. They also contained specific IgA to the virus as detected by indirect immunofluorescence. It is suggested that production of malignant catarrhal fever virus specific IgA in the nasal cavity, contributes to the elimination and cessation of the virus shed in the nasal secretions of wildebeest calves over 3 months. old.

Trypanosoma congolense and T vivax infections in cattle were shown to have a suppressive effect on the secondary humoral immune response to M mycoides. The trypanosome infections caused an involution of the thymus. The secondary response was biphasic in nature and was unrelated to infection with trypanosomes.

Zebu cattle infected with either Trypanosoma congolense EATRO 1800 or Trypanosoma vivax EATRO 1721 had suppressed humoral immune responses to Leptospira biflexa injected intravenously and to attenuated Brucella abortus injected subcutaneously. T. congolense infections were more suppressive than T. vivax infections. In cattle infected with T. vivax, the suppression of immune responses to both bacterial immunogens was abrogated when the animals were treated with Berenil at the time of antigen administration. In cattle infected with T. congolense, simultaneous Berenil treatment at the time of vaccination abolished the suppression of immune response to L. biflexa, and lessened but did not abrogate the suppression of immune response to B. abortus.

Only F38 isolates of mycoplasma cause classical contagious caprine pleuropneumonia (CCPP). Therefore, research has focused on the development of a vaccine that will prevent serious epidemics of the disease in goats. Goats immunized with two doses of a lyophilized preparation of isolated F38 organisms administered 4 weeks apart were completely immune to experimentally induced CCPP. The minimum immunizing dose was 0.15 mg, and this dose was still effective after storage for 14 months at 4 C and 22 C. The duration of immunity induced by a single dose of lyophilized F38 was at least 12 months.

The course of Trypanosoma brucei infection in the wildebeest (Connochaetes taurinus) was studied. A low but persistent parasitaemia developed in all five wildebeest following intravenous inoculation with 1 X 10(8) organisms of clone ILTat 2.1. Unlike cattle controls, however, the wildebeest did not develop anaemia. In both cattle and wildebeest, radioimmunoassay studies revealed a classical sequence of production of IgM, IgG1 and IgG2 antibodies which had the capacity to bind to the corresponding purified variable surface glycoprotein and to neutralize the infectivity of ILTat 2.1. Investigations into the interaction between post-infection sera, trypanosomes and freshly isolated peripheral blood leucocytes (PBL) of wildebeest and cattle showed that sera from the wildebeest had a higher capacity to induce adherence of trypanosomes to homologous PBL. The adherence and phagocytosis-inducing activity resided in the IgM fraction. Cross-testing of the antibodies and PBL revealed that wildebeest IgM antibodies induced high adherence indices when tested on cattle PBL. High adherence indices were also observed when cattle IgM antibodies were tested on PBL of wildebeest. It was concluded that the phagocytic system of the wildebeest was superior to that of cattle, that freshly prepared wildebeest PBL bear receptors for wildebeest as well as cattle IgM, and that cattle PBL bear a receptor for wildebeest IgM that would appear to be different from that for cattle IgM.

The genera Anaplasma, Ehrlichia, Cowdria, Neorickettsia and Wolbachia encompass a group of obligate intracellular bacteria that reside in vacuoles of eukaryotic cells and were previously placed in taxa based upon morphological, ecological, epidemiological and clinical characteristics. Recent genetic analyses of 16S rRNA genes, groESL and surface protein genes have indicated that the existing taxa designations are flawed. All 16S rRNA gene and groESL sequences deposited in GenBank prior to 2000 and selected sequences deposited thereafter were aligned and phylogenetic trees and bootstrap values were calculated using the neighbour-joining method and compared with trees generated with maximum-probability, maximum-likelihood, majority-rule consensus and parsimony methods. Supported by bootstrap probabilities of at least 54%, 16S rRNA gene comparisons consistently clustered to yield four distinct clades characterized roughly as Anaplasma (including the Ehrlichia phagocytophila group, Ehrlichia platys and Ehrlichia bovis) with a minimum of 96.1% similarity, Ehrlichia (including Cowdria ruminantium) with a minimum of 97.7% similarity, Wolbachia with a minimum of 95.6% similarity and Neorickettsia (including Ehrlichia sennetsu and Ehrlichia risticii) with a minimum of 94.9% similarity. Maximum similarity between clades ranged from 87.1 to 94.9%. Insufficient differences existed among E. phagocytophila, Ehrlichia equi and the human granulocytic ehrlichiosis (HGE) agent to support separate species designations, and this group was at least 98.2% similar to any Anaplasma species. These 16S rRNA gene analyses are strongly supported by similar groESL clades, as well as biological and antigenic characteristics. It is proposed that all members of the tribes Ehrlichieae and Wolbachieae be transferred to the family Anaplasmataceae and that the tribe structure of the family Rickettsiaceae be eliminated. The genus Anaplasma should be emended to include Anaplasma (Ehrlichia) phagocytophila comb. nov. (which also encompasses the former E. equi and the HGE agent), Anaplasma (Ehrlichia) bovis comb. nov. and Anaplasma (Ehrlichia) platys comb. nov., the genus Ehrlichia should be emended to include Ehrlichia (Cowdria) ruminantium comb. nov. and the genus Neorickettsia should be emended to include Neorickettsia (Ehrlichia) risticii comb. nov. and Neorickettsia (Ehrlichia) sennetsu comb. nov.