First detection of Rickettsia felis in Ctenocephalides felis fleas from Italy

Rickettsiales in Italy

There is no updated information on the spread of Rickettsiales in Italy. The purpose of our study is to take stock of the situation on Rickettsiales in Italy by focusing attention on the species identified by molecular methods in humans, in bloodsucking arthropods that could potentially attack humans, and in animals, possible hosts of these Rickettsiales. A computerized search without language restriction was conducted using PubMed updated as of December 31, 2020. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology was followed. Overall, 36 species of microorganisms belonging to Rickettsiales were found. The only species identified in human tissues were Anaplasma phagocytophilum,Rickettsia conorii, R. conorii subsp. israelensis, R. monacensis, R. massiliae, and R. slovaca. Microorganisms transmissible by bloodsucking arthropods could cause humans pathologies not yet well characterized. It should become routine to study the pathogens present in ticks that have bitten a man and at the same time that molecular studies for the search for Rickettsiales can be performed routinely in people who have suffered bites from bloodsucking arthropods.

Cats as potential mammalian reservoirs for Rickettsia sp. genotype RF2125 in Bangkok, Thailand

Rickettsia felis is an obligate intracellular alpha-proteobacteria and the cause of flea-borne spotted fever (FBSF), an emerging zoonosis of global public health importance, for which dogs and cats have been implicated as potential mammalian reservoirs hosts. The purpose of this study was to determine the prevalence and associated risk factors for R. felis-like species in semi-domesticated cats and their fleas in aim of understanding public health risks posed by cats and their fleas in Bangkok, Thailand. Single whole blood samples (n = 432) and where observed, fleas (n = 234), were collected from cats from 53 temple communities in Bangkok. Fleas were morphologically and genetically identified to a species level. Cat blood and fleas were subjected to a spotted fever group (SFG)-specific PCR targeting the partial outer membrane protein B (ompB). Those that were positive, were further characterised using an R. felis-specific nested PCR targeting the partial citrate synthase A (gltA) gene. All fleas were identified as Ctenocephalides felis felis. In total SFG Rickettsiae were detected in the blood of 82/482 (17.01%) cats and 3/234 fleas (1.28%). DNA sequencing of the partial ompB characterised all positive amplicons from cat blood and their fleas as 100% identical to Rickettsia endosymbiont of Ctenocephalides felis orientis isolate (Rickettsia sp. genotype RF2125) and Rickettsia asemboensis (GenBank accession no. KP256362 and KY650699, respectively). The gltA gene targeting R. felis was successfully amplified from 12/82 PCR-positive cat blood samples and these clustered with 99% bootstrap support with isolates within the Rickettsia sp. genotype RF2125 clade. Cats that were permitted to roam freely inside monasteries were more likely to be infected with R. felis compared with cats confined indoors. The results suggest that cats in Thailand are potential mammalian reservoir hosts for Rickettsia sp. genotype RF2125.

Molecular survey of Rickettsial organisms in ectoparasites from a dog shelter in Northern Mexico

The objective of this study was to screen and identify rickettsial organisms in ectoparasites collected from dogs in a shelter in Gomez Palacio, Durango, Mexico. One hundred dogs were inspected for ectoparasites. All the dogs were parasitized with Rhipicephalus sanguineus ticks, three with Heterodoxus spiniger lice and one with Ctenocephalides felis fleas. DNA was extracted from the ectoparasites found on each dog, and PCR with the primers for the Anaplasmataceae 16S rRNA and citrate synthase gltA genes were performed. Eight DNA samples obtained from ticks, three from lice and one from fleas were positive to 16S rRNA. Only one sample from C. felis and one from H. spiniger were positive to gltA. Sequence analysis of amplified products from C. felis showed identity to Rickettsia felis, Wolbachia pipientis, and Wolbachia spp., while a sequence from H. spiniger showed identity to Wolbachia spp. Herein we report the molecular detection of R. felis, W. pipientis, and Wolbachia spp. in C. felis and H. spiniger in northern Mexico. These results contribute to the knowledge of the microorganisms present in ectoparasites from dogs in Mexico.

Limited Evidence for Rickettsia felis as a Cause of Zoonotic Flea-Borne Rickettsiosis in Southern California

Over 90% of human flea-borne rickettsioses cases in California are reported from suburban communities of Los Angeles and Orange counties and are presumed to be associated with either Rickettsia typhi or Rickettsia felis infection. Ctenocephalides felis (Bouché) is considered the principal vector for both rickettsiae, and R. felis has largely replaced R. typhi as the presumptive etiologic agent based on the widespread incidence of R. felis in cat flea populations. However, with no evidence to confirm R. felis as the cause of human illness in southern California, coupled with recent findings that showed R. felis to be widespread in cat fleas statewide, we propose that this hypothesis should be reconsidered. Evidence of only limited numbers of R. typhi-infected cat fleas in the environment may indicate a very rare infection and explain why so few cases of flea-borne rickettsioses are reported each year in southern California relative to the population.

Rickettsia felis, an Emerging Flea-Borne Rickettsiosis

Rickettsia felis is an emerging insect-borne rickettsial pathogen and the causative agent of flea-borne spotted fever. First described as a human pathogen from the USA in 1991, R. felis is now identified throughout the world and considered a common cause of fever in Africa. The cosmopolitan distribution of this pathogen is credited to the equally widespread occurrence of cat fleas (Ctenocephalides felis), the primary vector and reservoir of R. felis. Although R. felis is a relatively new member of the pathogenic Rickettsia, limited knowledge of basic R. felis biology continues to hinder research progression of this unique bacterium. This is a comprehensive review examining what is known and unknown relative to R. felis transmission biology, epidemiology of the disease, and genetics, with an insight into areas of needed investigation.

A molecular survey of Rickettsia felis in fleas from cats and dogs in Sicily (Southern Italy)

Rickettsia felis, the agent of flea-borne spotted fever, has a cosmopolitan distribution. Its pathogenic role in humans has been demonstrated through molecular and serologic tests in several cases. The cat flea (Ctenocephalides felis) is considered the main reservoir and the biological vector. The aim of this study was to assess the presence and occurrence of R. felis in fleas collected from dogs and cats in various sites of Palermo (Sicily). Between August and October 2012, 134 fleas were collected from 42 animals: 37 fleas from 13 dogs and 97 fleas from 29 cats. Two species of fleas were identified: 132 Ctenocephalides felis (98.51%) collected on all animals and only two C. canis (1.49%) on one dog. Out of 132 C. felis, 34 (25.76%), 12 from dogs (32.43%) and 22 (22.68%) from cats, were positive for R. felis DNA by a polymerase chain reaction (PCR), confirmed by sequencing. The only two C. canis fleas were negative. About half of examined animals (47.62%, 20/42) were infested with at least one infected flea; in particular 46.15% of dogs (6/13) and 48.28% of cats (14/29). It seems that in the Palermo district there is a peri-domestic cycle, with a relatively high prevalence of R. felis infection in the cat flea, an insect widely diffused in home environments and which can frequently bite humans. The results also suggest that R. felis should be considered in the human differential diagnosis of any spotted-like fever or febrile illness without a clear source of infection in Sicily, especially if the patient is known to have been exposed to flea bites.

Molecular detection of Rickettsia felis and Bartonella henselae in dog and cat fleas in Central Oromia, Ethiopia

Fleas are important vectors of several Rickettsia and Bartonella spp. that cause emerging zoonotic diseases worldwide. In this study, 303 fleas collected from domestic dogs and cats in Ethiopia and identified morphologically as Ctenocephalides felis felis, C. canis, Pulex irritans, and Echidnophaga gallinacea were tested for Rickettsia and Bartonella DNA by using molecular methods. Rickettsia felis was detected in 21% of fleas, primarily C. felis, with a similar prevalence in fleas from dogs and cats. A larger proportion of flea-infested dogs (69%) than cats (37%) harbored at least one C. felis infected with R. felis. Rickettsia typhi was not detected. Bartonella henselae DNA was detected in 6% (2 of 34) of C. felis collected from cats. Our study highlights the likelihood of human exposure to R. felis, an emerging agent of spotted fever, and B. henselae, the agent of cat-scratch disease, in urban areas in Ethiopia.

Fleas infesting pets in the era of emerging extra-intestinal nematodes

Modifications in climatic conditions, movements of hosts and goods, changes in animal phenology and human behaviour and increase of wildlife, are presently concurring in the geographic spread of vectors and cardio-respiratory nematodes, e.g. Dirofilaria immitis, Angiostrongylus vasorum, Aelurostrongylus abstrusus and Capillaria aerophila. All these factors may also influence dispersion and clinical significance of fleas, thus posing relevant challenges in those regions where other parasites are emerging at the same time. Ctenocephalides felis, Ctenocephalides canis and Pulex irritans cause discomfort, nuisance, allergic reactions, anaemia, and may transmit several pathogens, some of them are of importance for public health. The present article reviews the importance of fleas in small animal practice and their sanitary relevance for dogs, cats and humans, and discusses current control methods in the present era of emerging extra-intestinal nematodes, towards a possible changing perspective for controlling key parasites affecting companion animals.

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.

Acquisition of Rickettsia felis by cat fleas during feeding

Evidence for horizontal routes of transmission for Rickettsia felis has come from detection of R. felis infection in vertebrates and multiple blood-feeding arthropods; however, infection of cat fleas, Ctenocephalides felis, during blood feeding has not been demonstrated. In this study, the ability of cat fleas to acquire R. felis through an infectious blood meal with subsequent vertical transmission was examined. Utilizing an artificial feeding system, Rickettsia-naive fleas were exposed to R. felis-infected blood meals and monitored for subsequent infection at weekly intervals for 4 weeks. At 7 days postexposure (dpe) ~52% of fleas successfully acquired rickettsiae and R. felis DNA; rickettsial transcript and DNA was detected in cat flea feces. Quantitative real-time polymerase chain reaction determined that both the R. felis infection load and R. felis infection density was significantly greater in fleas assessed at later time points. Although a persistent R. felis infection was detected in adult fleas, R. felis infection was not observed in F(1) progeny. This study demonstrates that cat fleas are able to acquire R. felis infection from an infectious blood meal and will serve as a model to examine R. felis transmission between arthropod and vertebrate hosts.

Canine and feline vector-borne diseases in Italy: current situation and perspectives

In Italy, dogs and cats are at risk of becoming infected by different vector-borne pathogens, including protozoa, bacteria, and helminths. Ticks, fleas, phlebotomine sand flies, and mosquitoes are recognized vectors of pathogens affecting cats and dogs, some of which (e.g., Anaplasma phagocytophilum, Borrelia burgdorferi, Dipylidium caninum, Leishmania infantum, Dirofilaria immitis, and Dirofilaria repens) are of zoonotic concern. Recent studies have highlighted the potential of fleas as vectors of pathogens of zoonotic relevance (e.g., Rickettsia felis) in this country. While some arthropod vectors (e.g., ticks and fleas) are present in certain Italian regions throughout the year, others (e.g., phlebotomine sand flies) are most active during the summer season. Accordingly, control strategies, such as those relying on the systematic use of acaricides and insecticides, should be planned on the basis of the ecology of both vectors and pathogens in different geographical areas in order to improve their effectiveness in reducing the risk of infection by vector-borne pathogens. This article reviews the current situation and perspectives of canine and feline vector-borne diseases in Italy.

Occurrence of Rickettsia felis in dog and cat fleas (Ctenocephalides felis) from Italy

Rickettsia felis is an obligate intracellular bacterium belonging to the spotted fever group, suspected to cause a murine typhus-like illness in humans, with a cosmopolitan distribution. This study was designed to estimate presence and occurrence of this pathogen in fleas collected from dogs and cats in different areas of Italy. Two species of fleas were identified, Ctenocephalides felis (80.3%) and Ctenocephalides canis (19.7%).

Overall, 320 fleas (257 C. felis and 63 C. canis) collected from 117 animals (73 dogs and 44 cats) were tested. Thirty-eight (11.9%) C. felis fleas, 13 from cats (17.6%) and 25 from dogs (10.2%) were positive for R. felis. No C. canis was positive. Fleas from cats showed a tendency to be more positive than fleas from dogs. Prevalence of R. felis among areas and within provinces of the same area was extremely variable, ranging from 0 to 35.3%. Overall, prevalence in north-eastern Italy (23.2%) was significantly higher than in south-western Italy (7.1%). This study confirmed the occurrence of R. felis in cat and dog fleas (C. felis) from Italy, similar to other European countries. The results also suggest that R. felis should be considered in the human differential diagnosis of any spotted-like fever in Italy, especially if the patient is known to have been exposed to flea bites.