Lack of susceptibility of Ehrlichia canis to imidocarb dipropionate in vitro.

In vitro antimicrobial susceptibility testing was used to compare the efficacy of imidocarb dipropionate and doxycycline on the growth of Ehrlichia canis in DH82 cell cultures. Over a 9-day period there were no significant differences (p < 0.01) in the growth of E. canis in untreated control wells and those to which imidocarb dipropionate was added at 1.2, 2.4, 4.8 or 12 micrograms/ml for the 1st 3 days. Average infection rates rose from 50 to 55% on day 0 to 100% on day 5 or 6. Doxycycline at 1 microgram/ml had residual or rickettsiocidal activity against E. canis with the average percentages of DH82 cells infected declining from 51 to 24% while the organism was exposed to the drug (3 days) and from 21 to 2% in the 6 days following removal of the drug from the cell culture medium.

Bartonella (Rochalimaea) henselae in southern Africa--evidence for infections in domestic cats and implications for veterinarians.

Substantial evidence has recently accumulated showing domestic cats to be the principal reservoirs of Bartonella henselae, the aetiological agent of human diseases including cat-scratch disease, bacillary angiomatosis, bacillary peliosis and a febrile bacteraemia syndrome. To determine the prevalence of antibodies reactive with Bartonella henselae in cats from southern Africa, indirect fluorescent antibody assays were carried out on feline sera from South Africa and Zimbabwe. Overall, 23% (39/171) of cats had antibody titres > or = 1/64, with cats from Zimbabwe (24%; 28/119) having higher seroprevalences than those from South Africa (21%; 11/52) although this difference was not statistically significant. The implications of these findings for veterinarians in southern Africa are discussed.

Intestinal permeability and function in dogs with small intestinal bacterial overgrowth.

Small intestinal bacterial overgrowth (SIBO) has been reported to occur commonly in dogs with signs of chronic intestinal disease. There are usually few intestinal histological changes, and it is uncertain to what extent bacteria cause mucosal damage. The aim of this study was to apply a differential sugar absorption test for intestinal permeability and function to the objective assessment of intestinal damage in dogs with SIBO. Studies were performed on 63 dogs with signs of chronic small and, or, large bowel disease, in which SIBO (greater than 10(5) total or greater than 10(4) anaerobic colony forming units/ml) was diagnosed by quantitative culture of duodenal juice obtained endoscopically. None of the dogs had evidence of intestinal pathogens, parasites, systemic disease or pancreatic insufficiency. differential sugar absorption was performed by determining the ratios of urinary recoveries of lactulose/rhamnose (L/R ratio, which reflects permeability) and D-xylose/3-O-methylglucose (X/G ratio, which reflects intestinal absorptive function) following oral administration. Dogs with SIBO comprised 28 different breeds, including 13 German shepherd dogs. SIBO was aerobic in 18/63 dogs (29 per cent), and anaerobic in 45/63 (71 per cent). Histological examination of duodenal biopsies showed no abnormalities in 75 per cent, and mild to moderate lymphocytic infiltrates in 25 per cent of the dogs. The L/R ratio was increased (greater than 0.12) in 52 per cent, and the X/G ratio reduced (less than 0.60) in 33 per cent of the dogs. Differential sugar absorption was repeated in 11 dogs after their four weeks of oral antibiotic therapy. The L/R ratio declined in all 11 dogs (mean +/- SD pre: 0.24 +/- 0.14; post: 0.16 +/- 0.11; P < 0.05), but changes in the X/G ratio were more variable. These findings show that SIBO is commonly associated with mucosal damage not detected on histological examination of intestinal biopsies, and that changes in intestinal permeability following oral antibiotics may be used to monitor response to treatment.

Rickettsia africae sp. nov., the etiological agent of African tick bite fever.

We propose the name Rickettsia africae sp. nov. (with type strain Z9-Hu) for a distinct species of spotted fever group (SFG) rickettsiae that is the etiological agent of African tick bite fever in humans. This rickettsia has a distinct natural cycle and can be phenotypically distinguished from the other SFG rickettsiae by microimmunofluorescence serotyping, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and by Western blotting (immunoblotting). Genotypic differences between R. africae and the other SFG rickettsiae can be demonstrated by PCR restriction fragment length polymorphism analysis, pulsed-field gel electrophoresis, and sequencing of the 16S rRNA gene.

Prevalence of rickettsia-like organisms and spotted fever group rickettsiae in ticks (Acari: Ixodidae) from Zimbabwe.

The prevalence of rickettsia-like organisms in ticks from Zimbabwe was determined using the hemolymph test. Amblyomma hebraeum had the highest prevalence of rickettsia-like organisms. Other species with rickettsia-like organisms included Amblyomma sparsum, Amblyomma variegatum, Hyalomma marginatum rufipes, Ripicephalus simus, Haemaphysalis leachi, Amblyomma rhinocerotis, and Hyalomma truncatum. Ticks with no demonstrable rickettsia-like organisms infection were Boophilus decoloratus, Haemaphysalis spinulosa, Rhipicephalus appendiculatus, Rhipicephalus evertsi evertsi, and Rhipicephalus sanguineus. Polymerase chain reaction followed by restriction fragment-length polymorphism analysis on samples of hemolymph-positive ticks showed the agent of African tick-bite fever to be present in A. hebraeum, Rickettsia conorii to be present in Rhipicephalus simus and Haemaphysalis leachi, and a spotted fever group rickettsia similar to that in Hyalomma marginatum marginatum ticks from Morocco and Portugal to be present in Hyalomma marginatum rufipes.

Ultrasonography of pancreatic neoplasia in the dog: a retrospective review of 16 cases.

The history, clinical signs and radiographic and ultrasonographic findings in 16 dogs with pancreatic neoplasia were reviewed retrospectively. Thirteen of the dogs had islet cell carcinoma compatible with insulinoma, one had a pancreatic adenocarcinoma and two had secondary invasion of the pancreas, one by a gastric carcinoma and one by an intestinal lymphoma. The clinical signs in the 13 dogs with insulinoma included collapse in 10 dogs, ataxia in seven, weakness in five, and seizures in two. Two of the 16 dogs had jaundice due to biliary obstruction by the primary tumour or metastases. The sensitivities for pancreatic neoplasia were three of 16 (19 per cent) for radiography and 12 of 16 (75 per cent) for ultrasonography; the sensitivities for metastasis were two of 11 (18 per cent) for radiography and six of 11 (55 per cent) for ultrasonography. Biliary obstruction was detected by ultrasonography in both affected dogs.

Further evidence for the efficacy of imidocarb dipropionate in the treatment of Ehrlichia canis infection.

Three dogs experimentally infected with Ehrlichia canis developed thrombocytopaenia and high antibody titres to E. canis in indirect fluorescent antibody tests. One dog also became leukopaenic. At Weeks 6 and 8 post-infection, the dogs were treated with imidocarb dipropionate (5 mg kg-1 subcutaneously) and a further dose was administered at Week 12 (5 mg kg-1 intramuscularly). Twelve weeks after the last treatment (post-treatment), all dogs had normal platelet counts which persisted for a further 10 weeks until the end of the experiment. The leukopaenia resolved 20 weeks post-treatment. Although antibody titres (< 1/5) to E. canis could not be detected prior to infection, titres of 1/2 560 to 1/5 120 developed by Week 6. By Week 8 post-treatment titres began to decline and by the end of the experiment were 5- to 6-fold serum dilutions lower (1/80 to 1/320). Sub-inoculation experiments 18 weeks post-treatment, failed to cause disease or stimulate antibody responses in susceptible dogs. Serology and sub-inoculation studies on 2 dogs experimentally infected with E. canis but not treated with imidocarb dipropionate, showed that these animals remained infected for the duration of the experiment. The results of these experiments confirm that imidocarb dipropionate is effective in the treatment of canine ehrlichiosis.

A new pathogenic spotted fever group rickettsia from Africa.

A spotted fever group (SFG) rickettsia was isolated in Zimbabwe from a patient with tick-bite, fever, headache and regional lymphadenopathy. A further six isolates were obtained from Amblyomma hebraeum ticks collected in Zimbabwe. These human and tick isolates were indistinguishable from each other, and from an Ethiopian SFG rickettsia, by microimmunofluorescence (MIF), sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), Western blotting and polymerase chain reaction followed by restriction fragment length polymorphism analysis (PCR-RFLP). They were, however, distinguishable from other SFG ricketsiae by MIF serotyping and in the case of the most closely related serotypes, Rickettsia conorii and the Israeli SFG rickettsia, by SDS-PAGE and Western blot. PCR-RFLP failed to distinguish between the Zimbabwean and Israeli SFG rickettsia, though each of these gave different digestion products from R. conorii. The Zimbabwean human and tick isolates and the Ethiopian SFG rickettsiae therefore represent a previously undescribed rickettsial serotype which apparently is pathogenic in human beings. It is proposed that the new serotype be named the agent of African tick-bite fever in order to distinguish it from R. conorii, which until now has been recognized as the only SFG rickettsia to infect man in Africa.

Reactivity of sera collected from dogs in Mutare, Zimbabwe, to antigens of Ehrlichia canis and Cowdria ruminantium.

Six of 20 sera from apparently healthy dogs in Mutare, Zimbabwe, contained antibodies which were reactive with Cowdria ruminantium and Ehrlichia canis in indirect fluorescent antibody tests at similar titres. In Western blots these sera recognised the immunodominant antigen bands of the two organisms. Sera with high titres (> 1/80) recognised additional antigen bands of each organism. It was not possible to determine whether these dogs had been exposed to C ruminantium, E canis or other Ehrlichia species. In areas where these organisms coexist serological tests for canine ehrlichiosis should be interpreted with caution.

Serological evidence for antigenic relationships between Ehrlichia canis and Cowdria ruminantium.

The sera from dogs experimentally infected with Ehrlichia canis reacted at very similar titres in indirect fluorescent antibody (IFA) tests with E canis and Cowdria ruminantium antigen. In Western blots these sera reacted strongly with the immunodominant antigens of E canis (27 kDa) and C ruminantium (25 and 32 kDa). The dogs experimentally infected with C ruminantium showed no clinical evidence of infection, though the presence of organisms in the blood was demonstrable, for up to two weeks after inoculation, by a polymerase chain reaction. The sera from these dogs were also reactive with both organisms in the IFA tests, but the antibody titres were four- to fivefold higher with C ruminantium than with E canis antigen. In Western blots, these sera reacted strongly with the 25 and 32 kDa antigens of C ruminantium but weakly with the 27 kDa antigen of E canis. These results provide strong evidence that the immunodominant antigens of E canis and C ruminantium contain cross-reacting epitopes.

Infections with Babesia canis and Ehrlichia canis in dogs in Zimbabwe.

Of 105 dogs examined at a veterinary hospital in Harare, Zimbabwe, 52 per cent had antibodies reactive with Ehrlichia canis in indirect fluorescent antibody tests, 26 per cent had Babesia canis parasites in peripheral blood smears and 17 per cent had both infections. None of the dogs with serological evidence of ehrlichiosis had typical E canis morulae detectable in blood smears. The infections were regarded as incidental findings not readily related to the reasons for examination in 46 per cent of the dogs with antibodies to E canis and 17 per cent of the dogs with both infections. The most common laboratory abnormalities were anaemia and thrombocytopenia and the prevalence and severity of these in concurrent infections were intermediate to those found in individual infections. There were no pathognomonic clinical signs or laboratory abnormalities which could be used to distinguish between individual and concurrent infections. However, there was a significantly higher prevalence of non-regenerative anaemia in dogs with antibodies to E canis than in dogs with both infections. The prevalence of thrombocytopenia was significantly higher in dogs with babesiosis than in dogs with antibodies to E canis and the prevalence of hyperglobulinaemia was significantly higher in dogs with both infections than in dogs with antibodies to E canis.

Western blot and indirect fluorescent antibody testing for antibodies reactive with Ehrlichia canis in sera from apparently healthy dogs in Zimbabwe.

Sera were collected from apparently healthy dogs in 3 major centres in Zimbabwe to establish the prevalence of antibodies reactive with Ehrlichia canis by indirect fluorescent antibody (IFA) testing at titres of 1/20 or greater. The overall seroprevalence was 42% (39/93) with dogs from Mutare (40%) and Harare (33%) having similar rates which were lower than those for Bulawayo (68%). The majority of the IFA positive dogs from Harare (67%) had no haematological or biochemical evidence of canine ehrlichiosis. Total protein, albumin and globulin values were determined in sera from blood collected from Bulawayo and Mutare and all values were within normal reference ranges. Western blot profiles of sera from dogs with IFA titres of greater than 1/160 were similar to those using sera from dogs experimentally infected with E. canis Oklahoma strain. Our results indicate that an organism which is antigenically very similar or identical to E. canis is present in Zimbabwe and that dogs are commonly exposed to this organism.

Q fever in Zimbabwe. A review of the disease and the results of a serosurvey of humans, cattle, goats and dogs.

Sera from 494 humans, 180 cattle, 180 goats and 27 dogs, collected from different regions of Zimbabwe, were examined by indirect fluorescence for antibodies reactive with phase II Coxiella burnetii antigen. Overall, 37% of humans were reactive at a titre of 1/40 or greater, and there was no evidence of age- or sex-related differences in seroprevalence. A review of clinical and epidemiological features of Q fever is presented in order to alert health workers to this infection, which apparently occurs frequently in Zimbabwe even though clinical cases have not been reported. In animals, serological evidence of Q fever infection was found in 39% of cattle, but only 15% of dogs and 10% of goats. These results suggest that cattle are important reservoirs of C. burnetii in Zimbabwe.

Pathogens in dog bite wounds in dogs in Harare, Zimbabwe.

Over a year swabs were taken from 87 untreated bite wounds in dogs seen by veterinary practitioners in Harare, Zimbabwe. Swabs were also taken from normal skin adjacent to the wound site, and gingival swabs were collected from normal dogs coming to the same clinics. The swabs were cultured aerobically for pathogens, particularly Staphylococcus intermedius, and the antibiotic sensitivities of the pathogens were determined by disc diffusion assay. The most common pathogens isolated from the wounds were S intermedius (23 per cent), Escherichia coli (18 per cent) and non-lactose-fermenting coliforms (14 per cent). S intermedius was common on the normal skin of the dogs with infected wounds, and was associated with wounds on the abdomen, hindlimbs and tail and wounds that were more than three days old. This organism was, however, isolated only infrequently from the gums and there was little correlation in general between the prevalence of pathogens in the mouth and their prevalence in wounds. Of the S intermedius isolates from wounds, 30 per cent were resistant to penicillin and multiple antibiotic resistance was common among the enterobacterial isolates. The majority of the pathogens were sensitive to cotrimoxazole.

Experimental infection of dogs with a Zimbabwean strain of Rickettsia conorii.

Seroconversion was demonstrated in dogs artificially infected with a Zimbabwean strain of Rickettsia conorii. No haematological or biochemical abnormalities were found and the only clinical signs observed were pain, erythema and oedema at the inoculation site and regional lymphadenopathy. Intermittent rickettsaemia was detected using the centrifugation shell vial technique up to 10 days post inoculation.