Arboviruses infecting people primarily exist in urban transmission cycles involving urban mosquitoes in densely populated tropical regions. For dengue, chikungunya, Zika and yellow fever viruses, sylvatic (forest) transmission cycles also exist in some regions and involve non-human primates and forest-dwelling mosquitoes. Here we review the investigation methods and available data on sylvatic cycles involving non-human primates and dengue, chikungunya, Zika and yellow fever viruses in Africa, dengue viruses in Asia and yellow fever virus in the Americas. We also present current putative data that Mayaro, o’nyong’nyong, Oropouche, Spondweni and Lumbo viruses exist in sylvatic cycles.

Rickettsia felis is a recently described flea-borne spotted fever group Rickettsia that is an emerging human pathogen. Although there is information on the organism from around the world, there is no information on the organism in China. We used a commercial ELISA to detect antibodies reactive against R. felis in blood samples and developed a PCR to detect the gltA of the organism in blood samples and external parasites. We found reactive antibodies in people (16%; 28/180), dogs (47%; 128/271) and cats (21%; 19/90) and positive PCRs with DNA from people (0.1%; 1/822), dogs (0.8%; 8/1,059), mice (10%; 1/10), ticks (Rhipicephalus sanguineus; 10%; 15/146), lice (Linognathus setosus; 16%; 6/37), fleas (Ctenocephalides felis felis; 95%; 57/60) and mosquitoes (Anopheles sinensis, Culex pipiens pallens; 6%; 25/428), but not from cats (0/135) or canine fecal swabs (0/43). This is the first report of R. felis in China where there is serological and/ or PCR evidence of the organism in previously reported [people, dogs, cats, ticks (Rhipicephalus sanguineus), fleas (Ctenocephalides felis felis) and mosquitoes (Anopheles sinensis, Culex pipiens pallens)] and novel species [mice and lice (Linognathus setosus)].

Although many vector-borne agents are potential zoonoses and cause substantial morbidity and mortality in dogs worldwide, there are limited data on these organisms in dogs of China. Quantitative PCRs for vector-borne agents were performed to investigate their prevalences in convenience whole blood samples obtained from 1114 dogs from 21 veterinary clinics and a commercial dog breeding facility in ten provinces of China. In addition, the PCRs were performed on 146 Rhipicephalus sanguineus senso lato and 37 Linognathus setosus collected from dogs in the commercial dog breeding facility. DNAs of Babesia gibsoni and B. vogeli (1.2 %), Ehrlichia canis (1.3 %), Hepatozoon canis (1.8 %) and Theileria orientalis (0.1 %) or a closely related organism were detected in the bloods of the dogs studied, and Babesia vogeli (3.4 %) and Ehrlichia canis (4.1 %) in R. sanguineus senso lato. The qPCRs for Anaplasma spp., Dirofilaria immitis and Leishmania spp. were negative for all blood samples, ticks and lice. At least one vector-borne agent was found in dogs from 5 of the 10 provinces investigated in this study. Overall, 4.4 % (49/1117) of the dogs studied were positive for at least one vector-borne agent with the prevalence being highest in the commercial breeding colony (24/97; 24.7 %). Our study confirms that B. vogeli, B. gibsoni, H. canis, and E. canis occur in China. Also, we present evidence that T. orientalis or a closely related organism can infect dogs.

We provide the first evidence that Bartonella quintana can infect dogs and cause typical signs of endocarditis. Using PCR and sequencing, we identified B. quintana in the blood of a dog from the United States with aortic valve endocarditis and probably also in the mitral valve of a dog from New Zealand with endocarditis.

Toxoplasma gondii is a zoonotic parasite of global importance. The outcome of infection in humans can depend on a number of factors including the infecting stage of the parasite, inoculating dose and virulence of the infecting strain. Molecular epidemiological studies have demonstrated an abundance of atypical strains of T. gondii in South America, many of which have been associated with more severe sequelae of infection. The aim of this study was to compare the virulence of T. gondii strains isolated in the Caribbean to a virulent Brazilian strain and an avirulent European strain. One hundred and twenty Swiss CD-1 mice were split into 8 groups of 15 mice and each group was inoculated with 200 tachyzoites of one of 8 isolates, comprising ToxoDB genotypes #1, #141, #265, #13, #3 and #6. Five mice per group were euthanized at day 8 post-inoculation (p.i.) and parasite burden was determined in heart, lungs and eyes using quantitative PCR. Lungs and brain were also examined by histopathology and immunohistochemistry. The remaining 10 mice per group were part of a survival experiment to assess virulence. DNA was extracted from tachyzoites of each of the 8 T. gondii isolates and genotyped at four ROP gene loci, including ROP5, ROP16, ROP17 and ROP18 to look for association with markers of virulence. Infection with ToxoDB genotype #13 from the Caribbean resulted in 100% of mice being euthanized which was comparative to infection with the virulent Brazilian strain (ToxoDB genotype #6). Significantly higher parasite burdens were recorded in the lungs and eyes of mice infected with ToxoDB genotypes #13 and #6. Genotyping of ROP loci revealed that the virulent Caribbean isolates had a different ROP18/ROP5 allelic profile (3/1) to the virulent Brazilian isolate (1/3); however, the avirulent Caribbean isolate (ToxoDB genotype #1) had the same ROP18/ROP5 profile as the avirulent European isolate (ToxoDB #3) (both 2/2). Caribbean isolates of intermediate virulence (ToxoDB #141 and #265) all had the same ROP18/ROP5 allelic profile (2/2). Isolates from the Caribbean with ToxoDB genotype #13 were acutely virulent for mice and comparable to a known virulent Brazilian isolate. The ROP protein allelic profile of the virulent Caribbean and Brazilian isolates differed indicating that perhaps other factors are involved in predicting virulence. Understanding virulence is important for predicting disease outcome in humans and may also aid vaccine design as well as drug discovery.

Theileria spp. are tick transmitted protozoa that can infect large and small ruminants causing disease and economic losses. Diagnosis of infections is often challenging, as parasites can be difficult to detect and identify microscopically and serology is unreliable. While there are PCR assays which can identify certain Theileria spp., there is no one PCR that has been designed to identify all recognized species that occur in ruminants and which will greatly simplify the laboratory diagnoses of infections. Primers and probes for a genus-specific pan-Theileria FRET-qPCR were selected by comparing sequences of recognized Theileria spp. in GenBank and the test validated using reference organisms. The assay was also tested on whole blood samples from large and small ruminants from nine provinces in China. The pan-Theileria FRET-qPCR detected all recognized species but none of the closely related protozoa. In whole blood samples from animals in China, Theileria spp. DNA was detected in 53.2% of the sheep tested (59/111), 44.4% of the goats (120/270) and 30.8% of the cattle (380/1,235). Water buffaloes (n = 29) were negative. Sequencing of some of the PCR products showed cattle in China were infected with T. orientalis/T. sergenti/T. buffeli group while T. ovis and T. luwenshuni were found in sheep and T. luwenshuni in goats. The prevalence of Theileria DNA was significantly higher in Bos p. indicus than in Bos p. taurus (77.7% vs. 18.3%) and copy numbers were also significantly higher (104.88 vs. 103.00Theileria 18S rRNA gene copies/per ml whole blood). The pan-Theileria FRET-qPCR can detect all recognized Theileria spp. of ruminants in a single reaction. Large and small ruminants in China are commonly infected with a variety of Theileria spp.