Prevalence of antibodies to spotted fever group rickettsiae in human beings and dogs from and endemic area of mediterranean spotted fever in Catalonia, Spain.

We assessed the prevalence of antibodies to spotted fever group rickettsiae in human beings and dogs by indirect immunofluorescence in the region of 'Vallés Occidental', Barcelona (Spain). In the group of 150 serum samples from patients without former history of Mediterranean spotted fever, 12 had antibodies to Rickettsia conori. The overall seroprevalence was 8% (95% confidence interval, 4.6% to 13.5%). There were no statistically significant differences between the mean ages of patients with positive and negative antibodies to R. conorii. However, seropositivity was significantly more common among patients living in semi-rural areas. In the group of 138 dog serum samples, 36 (26.1%) sera had antibodies to R. conorii. When the present results were compared with those obtained in a previous seroepidemiological survey carried out in the same geographical region in 1987, no significant differences were found. Therefore, although the epidemiological markers have dropped, this does not absolutely confirm the decrease of the presence of R. conorii in this area.

Porcine dermatitis and nephropathy syndrome in Spain.

In August 1995, the first case of porcine dermatitis and nephropathy syndrome was diagnosed in the north-eastern part of Spain; the pig showed characteristic dermal and renal lesions. Between then and January 1996, nine further animals from five different herds were diagnosed; they showed signs of anorexia, depression and, sometimes, pyrexia. Diarrhoea, Glässer's disease, conjunctivitis and gastric ulcers also occurred on the farms where the diagnoses were made. The affected pigs died of renal failure with diffuse fibrinous glomerulonephritis and a systemic necrotising vasculitis. Chronic interstitial nephritis, glomerulosclerosis and scar-like marks on the skin were observed in chronic cases. Other common findings in both acute and chronic cases were a diffuse depletion of lymph node lymphocytes with infiltration by syncytial cells (50 per cent of cases) and interstitial pneumonia. All the animals tested positive for porcine reproductive and respiratory syndrome virus (PRRSV) by serological tests and virus isolation. Serum urea and creatinine concentrations were above normal in the acutely affected animals. The pathogenesis of the condition is unknown but the lesions and immunopathological observations by other authors suggest that a type III hypersensitivity is a possible aetiology. The occurrence of PRRSV in these pigs suggests that the virus might be implicated in the pathogenesis of porcine dermatitis and nephropathy syndrome.

In vitro efficacy of several antimicrobial combinations against Brucella canis and Brucella melitensis strains isolated from dogs.

In vitro efficacy of tetracyclines, aminoglycosides, fluoroquinolones, rifampin and macrolides and their combinations against four Brucella canis and two B. melitensis strains isolated from dogs was evaluated by means of inhibition tests: minimal inhibitory concentration (MIC) and fractional inhibitory concentrations (FIC) and by bactericidal tests: minimal bactericidal concentrations (MBC) and kill-time experiments. In inhibition studies, tetracyclines showed the lowest MICs of all compounds tested (0.06-0.50 mg/l). However, doxycycline did not inhibit growth of B. canis D-519 strain at concentrations lesser than 1 mg/l. Most strains were resistant to macrolides. Chequerboard MIC titrations showed synergy between enrofloxacin and aminoglycosides against B. canis RM 6/66 reference strain and between doxycycline and streptomycin against B. canis D-519 strain. Combinations of tetracyclines and aminoglycosides were at the limit of synergy for B. canis RM 6/66 strain (FIC = 0.56). Combination of doxycycline and rifampin seemed to be antagonistic against B. canis M-strain (FIC = 3). Other combinations studied were indifferent or additive against all other strains. In bactericidal studies, aminoglycosides, fluoroquinolones and rifampin showed bactericidal activity at 1-4 x MIC but tetracyclines or macrolides did not kill brucellae below 8 x MIC. Results of kill-time experiments indicated that streptomycin was the antimicrobial agent tested which more rapid killed brucellae. In most cases, doxycycline did not kill brucellae in 96 h of incubation. Which using rifampin alone, some inocula of B. canis strains RM 6/66, D-519 and M- showed regrowth after 24 h of incubation. Retesting of these regrowing brucellae showed an increased MIC indicating development of phenotypic resistance. Testing of antimicrobial combinations in kill-time experiments indicated synergy between enrofloxacin and streptomycin and antagonism between rifampin and doxycycline both for B. canis RM 6/66 strain.

Use of indirect enzyme-linked immunosorbent assay with hot saline solution extracts of a variant (M-) strain of Brucella canis for diagnosis of brucellosis in dogs.

An ELISA, using hot saline solution extracts (HSS) of a less-mucoid variant (M-) strain of Brucella canis as antigen, was developed for detection of antibodies against B canis in dogs. The test was applied to 177 field serum samples previously tested by use of the 2-mercaptoethanol rapid slide agglutination test, 2-mercaptoethanol-tube agglutination test, and agar gel immunodiffusion containing HSS and cytoplasmic antigens of B. canis. Results indicated that this ELISA seems to be highly specific (95.6%) and slightly less sensitive (93.8%). The HSS obtained from B canis wild-type RM 6/66 also have been used, but in our study, it seemed to be unsuitable for use in ELISA because of the high background values observed for sera with negative test results.