Persistence of antibodies to Rickettsia conorii after an acute attack of boutonneuse fever

Ehrlichia canis and Rickettsia conorii Infections in Shelter Dogs: Seropositivity and Implications for Public Health

A cross-sectional study was conducted to gain insight into the epidemiology of canine ehrlichiosis and rickettsiosis in northern Portugal. Specific IgG antibodies to Ehrlichia canis were analysed using a commercial enzyme-linked immunosorbent assay (ELISA), and antibodies to Rickettsia conorii were analysed using a commercial indirect immunofluorescence antibody test (IFAT). A total of 113 dogs from two different shelters were sampled, and seroprevalence values of 0.9% (95% confidence (CI): 0.2-4.8%) for E. canis and 9.7 (95% CI: 5.5-16.6%) for R. conorii were found. Multiple logistic regression investigated risk factors for seropositivity. The odds ratios (ORs) of R. conorii seropositivity were higher for female dogs (OR = 6.429; 95% CI: 1.201-34.407). Dogs seropositive for co-infection (E. canis + R. conorii) were more frequently observed among females (OR = 7.606; CI 95%: 1.478-39.132) and in Shelter 2 (OR = 18.229; 95% CI: 2.190-151.756). These findings show that shelter dogs in northern Portugal are exposed to E. canis and R. conorii, which can affect both canines and humans. It is imperative to adopt a One Health approach to educate the public about the hazards of canine zoonoses and develop legislation and procedures to control their spread and preserve public health.

Prevalence of antibodies to Rickettsia conorii in human beings and dogs from Catalonia: a 20-year perspective

The incidence of Mediterranean spotted fever (MSF) in Catalonia (Spain) has decreased in the last two decades. The prevalence of antibodies to Rickettsia conorii in human beings and dogs in the region of Vallès Occidental (Catalonia) was assessed by indirect immunofluorescence, and the results compared with those obtained in a similar study from 1987. Nineteen (5·0%) out of 383 human serum samples had antibodies to R. conorii. This seroprevalence was significantly lower (11·5%) (P = 0·003) than that recorded in the 1987 survey. Forty-two out (42·0%) of 100 canine serum samples had antibodies to R. conorii. A high proportion of the studied dogs (91·0%) were receiving anti-tick treatment, mainly with permethrin-imidacloprid spot-on (Advantix, Bayer, Germany). The current canine seroprevalence was not significantly different from that recorded in the 1987 survey (36.9%). In conclusion, this study shows a significant decrease in the prevalence of antibodies to R. conorii in the human population of Catalonia in the last 20 years, which corresponds with a decrease in the number of cases of MSF. We suggest that the widespread use of anti-tick treatment in dogs could limit the introduction of ticks to humans due to a reduction of infestation duration in dogs, thus contributing to the decrease in MSF incidence.

Flinders Island spotted fever: a newly recognised endemic focus of tick typhus in Bass Strait. Part 2. Serological investigations

Twenty-six cases of a spotted-fever-like illness have been identified on Flinders Island, Tasmania, over a 17 year period. These patients and 335 healthy persons from the island were investigated serologically using the Weil-Felix agglutination test (Proteus sp. antigens OX2, OX19, OXK) and rickettsia-specific microimmunofluorescence. The antigens used in these latter tests comprised one member of the typhus group (Rickettsia typhi) and three members of the spotted fever group (Rickettsia rickettsii, Rickettsia australis and Rickettsia conorii). Patients with Flinders Island spotted fever showed a higher prevalence of positive reactions to the Weil-Felix tests (with OX2 and OX19 antigens) and a higher prevalence of positive results to rickettsia-specific serological tests (with the exception of antibodies to Rickettsia typhi) than did healthy persons; OX2 (36% v. less than 1%); OX19 (36% v. less than 1%); Rickettsia rickettsii (42% v. 1%); Rickettsia australis (46% v. 1%); Rickettsia conorii (42% v. 1%); Rickettsia typhi (4% v. 4%). In seven of the 26 patients (27%) seroconversion was demonstrated by means of Weil-Felix tests, confirming recent infection. In six of these patients seroconversion was also demonstrated in rickettsia-specific tests. Although these results support the clinical evidence that the illness on Flinders Island is caused by a rickettsia of the spotted fever group, the aetiological agent remains to be isolated.

The prevalence of IgG antibodies to spotted-fever group rickettsiae among urban and rural dwelling children in southern Israel

The prevalence of IgG antibodies to spotted-fever group rickettsiae was studied in a sample of 1,055 healthy children aged 2-17 years, residents of the desert Negev region of southern Israel. Groups of children from 5 different places of residency were tested: (1) urban children from the city of Beer-Sheva; (2) children from Omer, a suburb of the city; (3) children from rural communes ("kibbutz"); (4) children from small agricultural settlements ("moshav"); and (5) seminomadic bedouin children. Overall 40 sera (3.8%) were positive by the indirect immunofluorescent antibody assay at a titer of 40. The prevalence rate was 3.6% in males and 4.0% in females. Age-specific prevalence rates for the 2-5, 6-9, 10-13 and 14-17 year old groups were 2.0, 5.4, 4.1 and 3.6% respectively. The prevalence rates by place of residency were: urban 3.3%, suburban 3.3%, "kibbutz" 3.8%, "moshav" 5.1% and seminomadic children 3.3%, and did not differ by socio-economic status as measured by degree of crowding. The results indicate that spotted fever is endemic in all human habitats in the Negev region. Our data do not support association to sex or socio-economic status of the children tested. Lack of cumulative prevalence rates with increasing age suggests that antibodies may wane to undetectable levels in the years following the infection.

New trends in Mediterranean spotted fever

Mediterranean Spotted Fever is a disease caused by Rickettsia conorii. It is endemic to the Mediterranean area, where, for the last few years, the number of cases has increased, possibly due, in part, to climatic factors. The main clinical aspects of a prospective series of 246 cases diagnosed from 1983 to 1988 are presented. The most characteristic manifestations were fever, exanthema and tache noire. Other frequent manifestations were headache, myalgia and arthralgia, and with lesser frequency, hepatomegaly, splenomegaly, gastrointestinal symptoms and conjunctivitis. Notable analytical changes are the rise of hepatic and muscular enzymes in a large number of patients. In some cases we have found signs of myositis in muscular biopsy. The evolution of our patients was usually favorable though serious and even deadly forms of the disease have been described. One of the factors that seems to greatly influence the appearance of these forms is delay in the initiation of effective treatment.

Mediterranean spotted fever in Lombardy: an epidemiological, clinical and laboratory study of 76 cases in the years 1977-1986

This paper describes the epidemiological, clinical and laboratory features of 76 cases of Mediterranean spotted fever occurring during the years 1977-1986. The patients observed all lived in the Lombardy region of Italy, which is not located on the Mediterranean Basin. Our data show the highest prevalence of the disease, as reported by other authors, in southern regions of Italy, in the same years: 1979-1983. No differences were noted between age groups or sexes, and the late spring-summer seasonality was confirmed. The clinical signs and symptoms in our cases were those common to the disease. The microimmunofluorescence method was found to be more sensitive and specific than the Weil-Felix test for serological diagnosis. Finally, we showed that doxycycline and oxytetracycline both induce rapid remission of fever.

Laboratory diagnosis of boutonneuse fever by enzyme-linked immunosorbent assay

Little is known about the use of the enzyme-linked immunosorbent assay (ELISA) in the diagnosis of boutonneuse fever, and the reports which do exist have concerned the use of a strain of African origin and a peroxidase-labelled conjugate. We have used, as antigen, a Sicilian strain of Rickettsia conorii recently isolated from a patient with boutonneuse fever and anti-human immunoglobulins G and M labelled with alkaline phosphatase as conjugate. 432 (84.6%) of 500 sera from patients with boutonneuse fever, 4.4% of 384 sera from patients with various other pathologies, and 2.9% of 204 sera from blood donors gave positive reactions. The ELISA was highly sensitive and specific in the diagnosis of boutonneuse fever, and seems to be the test of choice for sero-epidemiological investigations, and when a large number of specimens must be examined. The test is more sensitive than the indirect immunofluorescence test, at least in the early stage of the disease (44.9% vs 21.3% positive respectively), and a long time after an acute attack.

Mediterranean spotted fever in Salamanca, Spain. Epidemiological study in patients and serosurvey in animals and healthy human population

Mediterranean spotted fever is a spotted fever group rickettsiosis caused by Rickettsia conorii. The fever has a recognized incidence in large geographic areas, and its presence in Salamanca Province (Spain) has been well documented since 1981. This work presents the results of the centralized prospective survey carried out in this area and was designed to study the epidemiological behavior of the disease and the prevalence of antibodies against R. conorii among animals and healthy human population. In 110 patients with confirmed diagnosis by an immunofluorescent antibody test we have observed a bimodal temporal curve of incidence of Mediterranean spotted fever in our zone and their predominant origin in villages under 2000 inhabitants. The serosurvey in a statistically representative sample of the human population of Salamanca shows a rate of 73.5% of reactive sera and percentages as high as 82% in samples from small villages. The seroepidemiological study of 300 animals reveals a widespread response to rickettsial antigens throughout the province. Immunofluorescent antibody titers of greater than or equal to 1:40 are present in 93% of dogs and high rates and titers are detected in other domestic mammals, suggesting their feasible epidemiological role in Mediterranean spotted fever.