The sensitivities of a PCR assay and a DNA probe assay were compared for the detection of Cowdria ruminantium in Amblyomma ticks that were fed on C. ruminantium-infected, clinically reacting, and recovered carrier animals. The PCR assay and DNA probe detected infection in 86.0 and 37.0%, respectively, of 100 ticks fed on a febrile animal. In 75 ticks fed on carrier animals, PCR and the DNA probe detected infection in 28.0 and 1.33% of ticks, respectively. This demonstrates that the DNA probe has poor sensitivity for the detection of low levels of infection in ticks and that PCR is necessary for this purpose. The PCR assay had a detection limit of between 1 and 10 C. ruminantium organisms and did not amplify DNA from Ehrlichia canis, which is phylogenetically closely related to C. ruminantium, Theileria parva, or uninfected Amblyomma hebraeum or A. variegatum. PCR detected infection in A. hebraeum and A. variegatum adult ticks infected with one of six geographically different C. ruminantium strains. Amplification was also possible from desiccated ticks and ticks fixed in 70% ethanol, 10% buffered formalin, or 2% glutaraldehyde. The PCR assay supersedes the DNA probe and older detection methods for the detection of C. ruminantium in ticks, particularly those fed on carrier animals, and is suitable for both prospective and retrospective studies which require accurate detection of C. ruminantium in individual ticks. Application of the PCR assay should significantly improve the understanding of heartwater epidemiology, particularly through the determination of field tick infection rates.
Front Cover Caption: The cover image is based on the Research Article High-resolution melting curve FRET-PCR rapidly identifies SARS-CoV-2 mutations by Subarna Barua et al., https://doi.org/10.1002/jmv.27139.
A study of the distribution of Culicoides species was conducted by establishing 12 light trap sites over five rainy seasons between 1998 and 2003 covering all the geo-climatic natural regions of Zimbabwe. In total, 279 919 specimens of Culicoides were trapped over a total of 163 trapping nights. The highest median counts of Culicoides per trapping night were recorded in natural region III, which has climatic conditions conducive to the successful development of the larvae. Culicoides imicola, the major vector of bluetongue and African horse sickness viruses in Africa, was found to be the most abundant species (80.4%), followed by Culicoides enderleini (5.9%) and Culicoides milnei (5.2%). This study identified 10 species of Culicoides that had not been previously described in Zimbabwe, including Culicoides loxodontis and Culicoides miombo, which are members of the C. imicola complex. A total of 23 994 Culicoides midges were collected from five trap sites in Harare, Zimbabwe, with the dominant species, C. imicola, representing 91.6% of the total collection. Seventeen arboviruses were isolated from these midges, 15 of which were bluetongue virus. The predominant bluetongue virus serotype was serotype 11, followed by serotypes 1, 8, 12 and 15. Bluetongue virus serotypes 1, 2, 8, 10, 12, 15, 16 and 18, detected in this study, had not been previously reported in Zimbabwe.
Among the 36 cases of brucellosis here reported there were 22 in which the diagnosis was based on actual culture of brucellar organisms and 14 in which it was based on serologic evidence alone. Twenty-nine patients were farmers, and the others had all come into contact somehow with meat or milk from infected herds. The course of brucellar osteomyelitis was chronic and it was the hardest of all lesions to treat successfully. Secondary invading organisms often appeared and sometimes persisted after cultures had become negative for Brucella. Spondylitis was frequent, and in 11 cases it was destructive. Most patients were treated with streptomycin and either tetracycline or sulfadiazine, vestibular function being tested periodically to detect early signs of injury to the eighth cranial nerve. For patients with brucellosis of the bones and joints the authors recommend aggressive surgical treatment.
Babesia spp. are tick-borne protozoan hemoparasites and the second most common blood-borne parasites of mammals, in particular domestic animals. We used the Clustal Multiple Alignment program and 18S rRNA gene sequences of 22 Babesia species from GenBank to develop a PCR that could detect a wide variety of Babesia spp. in a single reaction. The pan-Babesia FRET-qPCR we developed reliably detected B. gibsoni, B. canis, B. vogeli, B. microti, B. bovis, and B. divergens under controlled conditions but did not react with closely related species, mainly Hepatozoon americanum, Theileria equi, and Toxoplasma gondii.When we tested the pan-Babesia FRET-qPCR on DNA of whole blood from 752 cattle, sheep, goats, donkeys and horses from five Caribbean islands, we detected Babesia spp. expected to be present in the animals, mainly B. bovis and B. bigemina in cattle and B. caballi in horses and donkeys. Further, we found that animals were not uncommonly infected with species of Babesia usually associated with other hosts, mainly B. vogeli and B. gibsoni in cattle, sheep and goats, B. rossi in goats, and B. caballi in goats and sheep. Finally, the pan-Babesia FRET-qPCR enabled us to identify unknown species of Babesia in cattle, goats, sheep and donkeys.Overall, 70 % (525/752) of the animals we tested were positive confirming earlier limited studies that infections with Babesia spp. are common in livestock in the Caribbean.
The unique biology of flies and their omnipresence in the environment of people and animals makes them ideal candidates to be important vectors of antimicrobial resistance genes. Consequently, there has been increasing research on the bacteria and antimicrobial resistance genes that are carried by flies and their role in the spread of resistance. In this review, we describe the current knowledge on the transmission of bacterial pathogens and antimicrobial resistance genes by flies, and the roles flies might play in the maintenance, transmission, and surveillance of antimicrobial resistance.
To the Editor: The cat flea (Ctenocephalides felis felis Bouche, 1935) is a ubiquitous parasite of domestic and wild animals that also feeds readily on people. Recent studies have implicated the cat flea as a vector of new and emerging infectious diseases (1). To determine the pathogens in C. felis in New Zealand, we collected 3 cat fleas from each of 11 dogs and 21 cats at the Massey University Veterinary Teaching Hospital from May to June 2003. The fleas were stored in 95% alcohol until they were identified by using morphologic criteria and washed in sterile phosphate-buffered saline. The DNA from each flea was extracted individually by using the QiaAmp Tissue Kit (QIAGEN Ltd., Hilden, Germany), according to the manufacturer’s instructions. When polymerase chain reaction (PCR) was performed with primers for gltA and rOmpA as described (2), products were obtained with DNA from 15 (15%) of the fleas. The sequences of the products were identical to those of Rickettsia felis (GenBank {type:entrez-nucleotide,attrs:{text:AF191026,term_id:10441768,term_text:AF191026}}AF191026) with infected fleas taken from both dogs (3/11; 27%) and cats (7/21; 33%). When PCR was performed with primers for the 16S-23S rDNA interspacer region as described (3), products were obtained with DNA of four fleas. The sequences of the products from three fleas (from two cats) were identical to that of Bartonella henselae (GenBank {type:entrez-nucleotide,attrs:{text:AF312495,term_id:15277554,term_text:AF312495}}AF312495), and the sequence of the product of one flea (from a cat) was identical to that of B. clarridgeiae (GenBank {type:entrez-nucleotide,attrs:{text:AF167989,term_id:8117790,term_text:AF167989}}AF167989).
Our study is the first to identify R. felis in Oceania. The organism is a recently described human pathogen, and infections with this spotted fever group rickettsia have already been reported in 11 persons: 4 persons in the United States, 2 persons in Brazil, 4 persons in Europe, and 1 person in Thailand. The symptoms of the patients were nonspecific and included fever, headache, and rash. Diagnoses were made by sequencing products obtained by PCR with primers for the 17-kDa protein (4), citrate synthase (4), and PS 120 protein (5) genes. R. felis has been established in tissue culture (XTC-2 and Vero cells) (6), and serologic testing has been used to diagnose infections (5). Reports indicate that patients respond rapidly to doxycycline therapy (5), and in vitro studies have shown the organism is susceptible to rifampin, thiamphenicol, and fluoroquinolones.
B. henselae is an agent of cat-scratch disease, bacillary angiomatosis, bacillary peliosis, endocarditis, bacteremia, and various neurologic and ocular conditions. Cats are the reservoir hosts, and contact with cats and their fleas is an established risk factor for most infections. Although B. henselae has been isolated from 17% of domestic cats in New Zealand (7), only two human infections have been reported in the country; neuroretinitis was diagnosed in both patients (8). In neighboring Australia, however, cat-scratch disease, bacillary angiomatosis, and endocarditis have been diagnosed in numerous patients. Cats are also the reservoir hosts of B. clarridgeiae which has been implicated as an agent of cat-scratch disease in humans and aortic valve endocarditis and hepatic disease in dogs (9). The organism has been found in cat fleas (as great as 17%) in Europe (1), and although we found only one flea infected with B. clarridgeiae in New Zealand, this description is the first of the organism in Oceania. However, B. clarridgeiae has been found in domestic cats in nearby Indonesia and the Philippines (10).
Our findings add to the accumulating data on R. felis, B. henselae, and B. clarridgeiae and should alert medical workers in New Zealand, a common tourist destination, to the possibility that their patients may be infected with these organisms.
Background Although tick-borne diseases are important causes of morbidity and mortality in dogs in tropical areas, there is little information on the agents causing these infections in the Caribbean. Methodology We used PCRs to test blood from a cross-section of dogs on St Kitts for Ehrlichia (E.) canis, Babesia (B.) spp., Anaplasma (A.) spp. and Hepatozoon (H.) spp. Antibodies against E. canis and A. phagocytophilum/platys were detected using commercial immunochromatography tests. Records of the dogs were examined retrospectively to obtain clinical and laboratory data. Principal findings There was serological and/or PCR evidence of infections of dogs with E. canis (27%; 46/170), Babesia spp. (24%; 90/372) including B. canis vogeli (12%; 43/372) and B. gibsoni (10%; 36/372), A. platys (11%; 17/157) and H. canis (6%; 15/266). We could not identify the Babesia sp. detected in nine dogs. There was evidence of multiple infections with dual infections with E. canis and B. canis vogeli (8%; 14/179) or B. gibsoni (7%; 11/170) being the most common. There was agreement between immunochromatography and PCR test results for E. canis for 87% of dogs. Only 13% of exposed dogs had signs of a tick-borne disease and 38% had laboratory abnormalities. All 10 dogs presenting for a recheck after treatment of E. canis with doxycycline were apparently healthy although all remained seropositive and six still had laboratory abnormalities despite an average of two treatments with the most recent being around 12 months previously. Infections with Babesia spp. were also mainly subclinical with only 6% (4/67) showing clinical signs and 13% (9/67) having laboratory abnormalities. Similarly, animals with evidence of infections with A. platys and H. canis were largely apparently healthy with only occasional laboratory abnormalities. Conclusions Dogs are commonly infected with tick-borne pathogens in the Caribbean with most having no clinical signs or laboratory abnormalities.
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