A sero-epidemiological study of Rickettsia typhi infection in dogs from Soria province, central Spain

Epidemiological Study of the Occurrence of Typhus Group Rickettsia Natural Infection in Domiciliated Dogs from a Rural Community in South-Eastern Mexico

Simple Summary

Rickettsioses are relevant emergent and reemergent zoonoses in the Americas, including Mexico. Murine typhus caused by typhus group (TG) Rickettsia is prevalent in humans and their companion animals, such as dogs. This study found that 23.9% of the dogs (34/142) were infected by TG Rickettsia in Maxcanú, Yucatan (southeastern Mexico). Statistical analyses showed that reduced outdoor activities, age, sex and previous antiparasitic treatment are associated factors with less risk of TG Rickettsia infection in the sampled dogs. Monitoring and controlling these factors could help to restrict the enzootic transmission risk and prevent the potential zoonotic transmission.

Abstract

The aim is to describe the Typhus group (TG) Rickettsia infection in dogs and to identify factors associated with this infection. We collected blood samples and gathered exposure and clinical data of 142 dogs from a rural community of Yucatan. The Rickettsia group was determined by semi-nested PCR. Generalized linear models with binomial error distribution were used to model the associated factors from the dog sample for risk ratio (RR) estimation. Thirty-four dogs (23.9%) showed molecular evidence of TG Rickettsia DNA. The multivariate model showed that mixed-breed dogs (RR = 0.06) and dogs that had received antiparasitic treatment (RR = 0.049) had a lower risk of getting infected, taking as reference the purebred group and the non-treated dogs, respectively. Looking at variable interactions, adult dogs without outdoor activities had a lower infection risk than puppies (RR = 0.26). Among dogs with antiparasitic treatment, females had a higher infection risk than male dogs (RR = 26.2). The results showed enzootic TG Rickettsia circulation in dogs of a rural community. The factors outdoor activities, age and previous antiparasitic treatment, as well as the clinical variables signs of hemorrhages and epistaxis, were associated with a less chance of natural infection in the studied dogs. Prevention and control of the enzootic transmission risk of TG Rickettsia should help to reduce the potential zoonotic transmission of this pathogen.

Manifestations and Management of Flea-Borne Rickettsioses

Murine typhus and flea-borne spotted fever are undifferentiated febrile illnesses caused by Rickettsia typhi and Rickettsia felis, respectively. These organisms are small obligately intracellular bacteria and are transmitted to humans by fleas. Murine typhus is endemic to coastal areas of the tropics and subtropics (especially port cities), where rats are the primary mammalian host and rat fleas (Xenopsylla cheopis) are the vector. In the United States, a cycle of transmission involving opossums and cat fleas (Ctenocephalides felis) are the presumed reservoir and vector, respectively. The incidence and distribution of murine typhus appear to be increasing in endemic areas of the US. Rickettsia felis has also been reported throughout the world and is found within the ubiquitous cat flea. Flea-borne rickettsioses manifest as an undifferentiated febrile illness. Headache, malaise, and myalgia are frequent symptoms that accompany fever. The incidence of rash is variable, so its absence should not dissuade the clinician to consider a rickettsial illness as part of the differential diagnosis. When present, the rash is usually macular or papular. Although not a feature of murine typhus, eschar has been found in 12% of those with flea-borne spotted fever. Confirmatory laboratory diagnosis is usually obtained by serology; the indirect immunofluorescence assay is the serologic test of choice. Antibodies are seldom present during the first few days of illness. Thus, the diagnosis requires acute- and convalescent-phase specimens to document seroconversion or a four-fold increase in antibody titer. Since laboratory diagnosis is usually retrospective, when a flea-borne rickettsiosis is considered, empiric treatment should be initiated. The treatment of choice for both children and adults is doxycycline, which results in a swift and effective response. The following review is aimed to summarize the key clinical, epidemiological, ecological, diagnostic, and treatment aspects of flea-borne rickettsioses.

Risk Factors for Scrub Typhus, Murine Typhus, and Spotted Fever Seropositivity in Urban Areas, Rural Plains, and Peri-Forest Hill Villages in South India: A Cross-Sectional Study

Scrub typhus and spotted fever group rickettsioses are thought to be common causes of febrile illness in India, whereas they rarely test for murine typhus. This cross-sectional study explored the risk factors associated with scrub typhus, tick-borne spotted fever, and murine typhus seropositivity in three different geographical settings, urban, rural, and hill villages in Tamil Nadu, South India. We enrolled 1,353 participants living in 48 clusters. The study included a questionnaire survey and blood sampling. Blood was tested for Orientia tsutsugamushi (scrub typhus), Rickettsia typhi (murine typhus), and spotted fever group Rickettsia IgG using ELISA. The seroprevalence of scrub typhus, spotted fever, and murine typhus were 20.4%, 10.4%, and 5.4%, respectively. Scrub typhus had the highest prevalence in rural areas (28.1%), and spotted fever was most common in peri-forested areas (14.9%). Murine typhus was more common in rural (8.7%) than urban areas (5.4%) and absent in peri-forested hill areas. Agricultural workers had a higher relative risk for scrub typhus, especially in urban areas. For murine typhus, proximity to a waterbody and owning a dog were found to be major risk factors. The main risk factors for spotted fever were agricultural work and living in proximity to a forest. Urban, rural plains, and hill settings display distinct epidemiological pattern of Orientia and rickettsial infections. Although scrub typhus and spotted fever were associated with known risk factors in this study, the findings suggest a different ecology of murine typhus transmission compared with other studies conducted in Asia.

Molecular evidence of Rickettsia typhi infection in dogs from a rural community in Yucatán, México

INTRODUCTION

Rickettsia typhi causes murine or endemic typhus, which is transmitted to humans primarily through flea bites contaminated with feces. Synanthropic and domestic animals also contribute to the infection cycle of R. typhi. Cases of murine typhus in humans were reported in the rural community of Bolmay, Yucatán, México, between 2007 and 2010. 

OBJECTIVE

To identify the presence of R. typhi and estimate the frequency of infection in dogs from Bolmay, México, a locality with previous reports of murine typhus in humans. 

MATERIALS AND METHODS

Whole blood samples were taken from 128 dogs. Total DNA was extracted for use in the polymerase chain reaction (PCR) to amplify fragments of the 17 kDa and omp B genes and confirms the presence of Rickettsia spp. The reaction products were sequenced, and alignment analysis was performed using the BLAST tool. 

RESULTS

The frequency of R. typhi infection in dogs was 5.5 % (7/128). The alignment identified 99% and 100% homology to the R. typhi 17 kDa and omp B genes, respectively. 

CONCLUSION

We confirmed the presence of R. typhi in dogs in the studied community but at a low frequency. However, there is potential risk of transmission to humans.

Antibodies to Rickettsia spp. and Borrelia burgdorferi in Spanish Wild Red Foxes (Vulpes vulpes)

We examined 314 red foxes (Vulpes vulpes) from the province of Soria, Spain, for Rickettsia typhi, Rickettsia slovaca, and Borrelia burgdorferi infection. Immunofluorescence assays showed 1.9% had antibodies to R. typhi, 6.7% had antibodies to R. slovaca, and 8.3% had antibodies to B. burgdorferi. Serostatus was not correlated with sex or age. Because red foxes can be infected by Rickettsiae and B. burgdorferi, presence of red foxes may be and indicator for the presence of these pathogens.

Molecular and serological study of rickettsial infection in humans, and in wild and farm animals, in the province of Burgos, Spain

Limited information is available on the presence of rickettsial infection in humans and animal reservoirs in Spain. Exposure to spotted fever group rickettsia in healthy humans and in farm and wild animals in the Province of Burgos, Spain, was examined by serological methods. Rickettsial DNA was also sought by PCR in animal samples. Of 102 human serum samples examined by indirect immunofluorescence assays (IFA), 5.88% were positive for antibodies against Rickettsia conorii (titers 1/128-1/512). Significant differences were detected in human seroprevalence with respect to age. In further IFAs, 102 out of 375 (27.2%) serum samples from the wild animals reacted with R. conorii antigens (titers 1/64-1/1024); 32 out of 281 (11.38%) samples from farm animals were also positive for R. conorii (titers 1/64-1/2048). The prevalence detected among total wild animals was significantly higher than among total farm animals. No rickettsial DNA was found by PCR in any farm or wild animal sample.

Murine typhus in central Greece: epidemiological, clinical, laboratory, and therapeutic-response features of 90 cases

OBJECTIVES

To document and evaluate the clinico-epidemiological profile of murine typhus during the re-emergence of the disease in a previously endemic focus in central Greece.

METHODS

This was a 5-year, hospital-based, observational study, in which 90 adult patients with murine typhus were prospectively identified and studied.

RESULTS

Most cases of the disease occurred in rural (52%) and semi-urban (34%) settings, with a seasonal frequency peak during the late summer. The triad of fever, headache, and rash was present in 64% of the patients within 2 days of hospital admission. Normal white blood cell counts (63%), thrombocytopenia (81%), and a high erythrocyte sedimentation rate (93%) were the main hematological findings upon presentation. Elevated aminotransferases (>84%), hypoalbuminemia (81%), and hyponatremia (36%) were prominent biochemical abnormalities. Pulmonary, neurological, and renal complications were noted in 26% of the patients and subsided after specific treatment. The duration of fever was shorter in patients treated with doxycycline (median 3 days) compared to ofloxacin (p=0.001) or doxycycline plus ofloxacin (p=0.009).

CONCLUSIONS

Murine typhus has the potential to cause significant morbidity. Awareness of the disease in endemic areas, early recognition of its clinical and laboratory features, and prompt administration of effective treatment are key factors to prevent potentially severe complications.

Fleas as parasites of the family Canidae

Historically, flea-borne diseases are among the most important medical diseases of humans. Plague and murine typhus are known for centuries while the last years brought some new flea-transmitted pathogens, like R. felis and Bartonella henselae. Dogs may play an essential or an accidental role in the natural transmission cycle of flea-borne pathogens. They support the growth of some of the pathogens or they serve as transport vehicles for infected fleas between their natural reservoirs and humans. More than 15 different flea species have been described in domestic dogs thus far. Several other species have been found to be associated with wild canids. Fleas found on dogs originate from rodents, birds, insectivores and from other Carnivora. Dogs therefore may serve as ideal bridging hosts for the introduction of flea-borne diseases from nature to home. In addition to their role as ectoparasites they cause nuisance for humans and animals and may be the cause for severe allergic reactions.

Seroepidemiological study of Rickettsia felis, Rickettsia typhi, and Rickettsia conorii infection among the population of southern Spain

Rickettsia typhi and Rickettsia conorii, the etiologic agents of, respectively, murine typhus and Mediterranean spotted fever, are recognized as frequent causes of fever of intermediate duration in southern Spain; in addition, in recent years Rickettsia felis has been detected in potential vectors in this area. Nevertheless, limited data exist regarding the actual prevalence of past infection due to these three pathogens. In the present study, the prevalence of past infection due to R. felis, R. typhi, and R. conorii was determined in a representative population of southern Spain during 2002. In addition, the possible risk factors associated with exposure to these pathogens were investigated. An epidemiological survey was completed by all subjects included in the study. Serum samples were tested by indirect immunofluorescence assay. The prevalence of past infection due to R. felis, R. typhi, and R. conorii among the 504 total subjects was 6.5, 3.8 and 8.7%, respectively. In multivariate analysis, infection due to R. felis was independently associated with a high-risk occupation (one that required working outdoors in nature, close contact with domestic animals, or potential contact with rodents) (OR=5.8; 95%CI 2.1-15.6), while infection due to R. typhi was associated with older age (factor of 1.04 [95%CI 1.008-1.068]) and frequent insect bites (OR=10.3; 95%CI 2.3-45.5). Two factors were associated with infection due to R. conorii: a high-risk occupation (OR=9.3; 95%CI 3.7-23.2), and participation in outdoor activities (OR=7.2; 95%CI 1.4-38.5). The results confirm the widespread prevalence of past infection due to R. felis, R. typhi, and R. conorii in the population of southern Spain.

Epidemiological study of Rickettsia typhi infection in two provinces of the north of Spain: analysis of sera from the general population and sheep

Data relating to Rickettsia typhi infection in Spain are scarce. A serological survey of 383 serum samples (184 males, 199 females) from the general population and 120 sera from sheep were studied by immunofluorescence assay (IFA). The human serum samples were collected from the general population of Palencia and Burgos provinces, and sheep serum samples were collected from Palencia province. Of the 383 human serum samples studied, 29 were positive for antibodies against R. typhi (7.5%) No statistical differences were found according to age, sex, origin (rural vs. urban) or geographic distribution, but a significant difference was observed related to occupation. In addition, 69 serums were found positives for R. typhi in sheep samples (57.5%). Our results indicated the circulation of R. typhi infectious for humans and sheep in Palencia and Burgos provinces. This study indicates that sheep may be infected with R. typhi, and that animals can, therefore be used as indicators of the presence of this organism.

Enfermedades producidas por Rickettsia

Species of the genus Rickettsia are small, obligate intracelular, gramnegative bacteria, many of which are considered nowadays a paradigm of emergent pathogens. With the exception of R. prowazekii, they are maintained in the natural environment through a cycle involving different hosts (mainly mammals), and arthropod vectors (in general ticks, and fleas); humans are affected only by incidental transmission due to arthropod bites. The common pathogenesis of these diseases lie on the predominantly infection of endotelial cells, that determines the development of multisistemic small vessel vasculitis, which may affect lungs (interstitial pneumonitis), heart (miopericarditis), skin (rash), central nervous system (meningoencephalitis), as well as liver, and kidneys. They are classified in two groups: spotted-fever group, and typhus group rickettsia. In Spain the most prevalent rickettsioses of both groups are mediterranean spotted fever (caused by R. conorii), and murine typhus (caused by R. typhi), respectively. This review focuses mainly in these two diseases, and also in other rickettsioses of interest due to their recently emergence or reemergence (R. slovaca, R. africae, R. prowazekii, R. felis), or to their high incidence in other areas (R. rickettsii, Orientia tsutsugamushi).