Seasonal distribution and environmental parameters associated with Brugia pahangi and Dirofilaria immitis in naturally infected dogs in Bangkok and vicinity, Thailand.

Dirofilaria immitis and Brugia pahangi are vector-borne parasites found in dogs and cats, including Thailand. In order to evaluate the effects of season and environmental parameters on the prevalence of these parasites, this retrospective study was conducted in 2019. A total of 79,506 canine blood samples were examined. B. pahangi was found in 0.55% of samples (438/79,506; 95% CI 0.50-0.61) while D. immitis was detected in 0.43% (345/79,506; 95% CI 0.39-0.48). One-way ANOVA found no effect of seasonal conditions on prevalence. For B. pahangi, the parameters rainfall, relative humidity and sunshine hours showed associations with p ≤ 0.20 and were included in multiple logistic regressions resulting in adjusted odds ratios of 0.53, 1.31 and 0.55, respectively. For D. immitis, only average temperature showed p ≤ 0.20, resulting in an odds ratio of 0.42. In conclusion, Thailand has environmental parameters that do not change very much during the year, so they might not affect the prevalence of two filarial nematodes. However, the threat of B. pahangi and D. immitis should not be ignored, especially in subtropical regions where their vectors are abundant. Both owners and veterinarians should be concerned about filarial prevention and control of D. immitis and B. pahangi.

Detection of Babesia canis vogeli and Hepatozoon canis in canine blood by a single-tube real-time fluorescence resonance energy transfer polymerase chain reaction assay and melting curve analysis.

A real-time fluorescence resonance energy transfer polymerase chain reaction (qFRET PCR) coupled with melting curve analysis was developed for detection of Babesia canis vogeli and Hepatozoon canis infections in canine blood samples in a single tube assay. The target of the assay was a region within the 18S ribosomal RNA gene amplified in either species by a single pair of primers. Following amplification from the DNA of infected dog blood, a fluorescence melting curve analysis was done. The 2 species, B. canis vogeli and H. canis, could be detected and differentiated in infected dog blood samples (n = 37) with high sensitivity (100%). The detection limit for B. canis vogeli was 15 copies of a positive control plasmid, and for H. canis, it was 150 copies of a positive control plasmid. The assay could simultaneously distinguish the DNA of both parasites from the DNA of controls. Blood samples from 5 noninfected dogs were negative, indicating high specificity. Several samples can be run at the same time. The assay can reduce misdiagnosis and the time associated with microscopic examination, and is not prone to the carryover contamination associated with the agarose gel electrophoresis step of conventional PCR. In addition, this qFRET PCR method would be useful to accurately determine the range of endemic areas or to discover those areas where the 2 parasites co-circulate.

Detection of Ehrlichia canis in canine blood samples by real-time fluorescence resonance energy transfer (FRET) PCR and melting curve analysis.

Ehrlichia canis is a small pleomorphic gram-negative, coccoid, obligatory intracellular bacterium and the cause of canine monocytic ehrlichiosis. A real-time fluorescence resonance energy transfer polymerase chain reaction (real-time FRET PCR) coupled with melting curve analysis was established for detection of E. canis infection in canine blood samples. The VirB9 gene was amplified using one pair of primers and the melting curve analysis was generated by heating the hybridizing probes and amplified products. Eight E. canis-infected dog blood samples were initially identified using the Giemsa staining/microscopic method followed by conventional PCR (cPCR)/Sanger sequencing for confirmation. The sensitivity and specificity of the real-time FRET PCR detection were 87.5% and 100%, respectively and the limit of detection was 6.6 x 10(3) copies of positive E. canis control plasmids. The real-time FRET PCR with melting curve analysis reported here is better than microscopic visualization or cPCR because the method is not affected by the false bias inherent in the microscopic method. Furthermore, many samples can be processed rapidly at the same time. This convenient tool is beneficial as an alternative assay for the epidemiologic study of canine ehrlichiosis as well as for eradication of these organisms in prevention and control programs in endemic areas.

High throughput pyrosequencing technology for molecular differential detection of Babesia vogeli, Hepatozoon canis, Ehrlichia canis and Anaplasma platys in canine blood samples.

Canine babesiosis, hepatozoonosis, ehrlichiosis, and anaplasmosis are tick-borne diseases caused by different hemopathogens. These diseases are causes of morbidity and mortality in dogs. The classic method for parasite detection and differentiation is based on microscopic observation of blood smears. The limitations of the microscopic method are that its performance requires a specially qualified person with professional competence, and it is ineffective in differentiating closely related species. This study applied PCR amplification with high throughput pyrosequencing for molecular differential detection of the following 4 hemoparasites common to tropical areas in dog blood samples: Babesia vogeli, Hepatozoon canis, Ehrlichia canis, and Anaplasma platys. PCR was initially used to amplify specific target regions of the ribosomal RNA genes of each parasite using 2 primer pairs that included 18S rRNA for protozoa (B. vogeli and H. canis) and 16S rRNA for rickettsia (E. canis and A. platys). Babesia vogeli and H. canis were discriminated using 9 nucleotide positions out of 30 base pairs, whereas E. canis and A. platys were differentiated using 15 nucleotide positions out of 34 base pairs that were determined from regions adjacent to 3' ends of the sequencing primers. This method provides a challenging alternative for a rapid diagnosis and surveillance of these tick-borne diseases in canines.

Comparative efficacy of a spot-on formulation containing emodepside and praziquantel (Profender ®, Bayer) and praziquantel and pyrantel oral tablets (Drontal ® for Cats) against experimental Ancylostoma ceylanicum infections in cats.

Ancylostoma ceylanicum is a common zoonotic hookworm of dogs and cats throughout Asia and has also been reported to occur within the Australasian region. The aim of this study to was to determine the efficacy of a spot-on formulation containing emodepside and praziquantel (Profender(®), Bayer) and praziquantel and pyrantel oral tablets (Drontal(®) for Cats, Bayer) against experimental A. ceylanicum infections in cats. Twenty-four kittens were each subcutaneously injected with 100 infective third-stage larvae of A. ceylanicum. Kittens were stratified by egg count and randomly allocated equally into control and two treatment groups. The first group were treated with emodepside 2.1%/praziquantel 8.6% (Profender®, Bayer) at the recommended label dose. The second group was treated with 80 mg pyrantel and 20mg praziquantel (Drontal(®) for Cats, Bayer) at the recommended label dose. The kittens in the control group were not treated. Egg counts were performed daily until the end of the study period and compared for the treated and control groups. No eggs were detected in the treated group of kittens within 4 days of treatment and faecal samples from this group remained negative throughout the rest of the study, resulting in a treatment efficacy (egg reduction) of 100% (P<0.0001). The egg counts remained high (993 ± 666 epg) in the untreated control group for the rest of the study period. This study demonstrated that both combination products containing topical emodepside/praziquantel (Profender(®), Bayer) and praziquantel/pyrantel oral tablets (Drontal(®) for Cats, Bayer) given at the recommended dose is highly effective against infection with A. ceylanicum in cats.

Rapid detection and identification of Wuchereria bancrofti, Brugia malayi, B. pahangi, and Dirofilaria immitis in mosquito vectors and blood samples by high resolution melting real-time PCR.

A simple, rapid, and high-throughput method for detection and identification of Wuchereria bancrofti, Brugia malayi, Brugia pahangi, and Dirofilaria immitis in mosquito vectors and blood samples was developed using a real-time PCR combined with high-resolution melting (HRM) analysis. Amplicons of the 4 filarial species were generated from 5S rRNA and spliced leader sequences by the real-time PCR and their melting temperatures were determined by the HRM method. Melting of amplicons from W. bancrofti, B. malayi, D. immitis, and B. pahangi peaked at 81.5±0.2℃, 79.0±0.3℃, 76.8±0.1℃, and 79.9±0.1℃, respectively. This assay is relatively cheap since it does not require synthesis of hybridization probes. Its sensitivity and specificity were 100%. It is a rapid and technically simple approach, and an important tool for population surveys as well as molecular xenomonitoring of parasites in vectors.

Successful treatment of Brugia pahangi in naturally infected cats with ivermectin.

Lymphatic filariasis is a common parasitic disease of cats in tropical regions including Thailand. The objective of this study was to determine the efficacy of ivermectin against microfilariae of Brugia pahangi in naturally infected cats. Eight cats naturally infected with B. pahangi were divided into control (untreated) and treated groups. Cats in the latter group were given ivermectin injection at 400 µg/kg weekly for 2 months. Microfilariae were counted every week until 48 weeks. Microfilaremia was significantly decreased in the treated group 4 weeks after starting the treatment and become zero at week 9 and afterwards. On the other hand, cats in the control group had high microfilaremia throughout the study. It was successful to treat and control B. pahangi infection in naturally infected cats using ivermectin.

Efficacy of a spot on combination containing imidacloprid 10% and moxidectin 1% (Advocate(®)/Advantage(®) Multi, Bayer Animal Health) against Ancylostoma ceylanicum in cats.

Ancylostoma ceylanicum is a common zoonotic hookworm of dogs and cats, especially in the Asia-Pacific region. The objective of this study was to determine the efficacy of a spot on combination product containing imidacloprid 10% and moxidectin 1% (Advocate(®)/Advantage(®) Multi, Bayer Animal Health) against A. ceylanicum in experimentally infected cats. Sixteen kittens were each subcutaneously injected with 100 infective third-stage larvae of A. ceylanicum. Kittens were stratified by egg count and randomly allocated into control and treatment groups. The kittens in the treatment group were each treated with a spot on combination of 10% (w/v) imidacloprid and 1% (w/v) moxidectin, administered topically at recommended label dose rates. The kittens in the control group were not treated. Egg counts were performed daily until the end of the study period and compared for the treated and control groups. No eggs were detected in the treated group of kittens within 4 days of treatment and faecal samples from this group remained negative throughout the rest of the study, resulting in a treatment efficacy (egg reduction) of 100% (P<0.0001). The egg counts remained high (993 ± 666 epg) in the untreated control group for the rest of the study period. This study demonstrated that based on faecal egg count reduction, the spot on combination containing imidacloprid 10% (w/v) and moxidectin 1% (w/v) (Advocate(®)/Advantage(®) Multi, Bayer Animal Health) given at the recommended dose is highly effective against infection with A. ceylanicum in cats.

Serological survey of Toxoplasma gondii, Dirofilaria immitis, Feline Immunodeficiency Virus (FIV) and Feline Leukemia Virus (FeLV) infections in pet cats in Bangkok and vicinities, Thailand.

The seroprevalence of Toxoplasma gondii, Dirofilaria immitis (heartworm), feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) infections was examined using serum or plasma samples from 746 pet cats collected between May and July 2009 from clinics and hospitals located in and around Bangkok, Thailand. The samples were tested for heartworm, FIV, and FeLV using a commercial ELISA. Of the 746 samples, 4.6% (34/746) were positive for heartworm antigen, 24.5% (183/746) had circulating FeLV antigen, and 20.1% (150/746) had antibodies against FIV. In addition, the first 348 submitted samples were tested for T. gondii antibodies using a modified agglutination test (MAT, cut off 1:25); 10.1% (35/348) were seropositive. Of the 348 cats sampled for all four pathogens, 11, 10, and 1 were positive for T. gondii antibodies and FIV antibodies, FeLV antigen, or D. immitis antigen, respectively. Of the 35 T. gondii-seropositive cats, 42.9% (15/35) were co-infected with at least one of the other three pathogens. The presence of antibodies to FIV was significantly associated with both age and gender, while FeLV antigen presence was only associated with age. In the case of FIV, males were twice as likely to be infected as females, and cats over 10 years of age were 13.5 times more likely to be infected than cats less than 1 year of age. FeLV antigen was more common in younger cats, with cats over 10 years of age being 10 times less likely to be FeLV positive than cats under 1 year of age. This is the first survey for these four pathogens affecting feline health in Thailand.

Experimental infection with Ancylostoma ceylanicum in dogs and efficacy of a spot on combination containing imidacloprid 10% and moxidectin 2.5% (Advocate/Advantage Multi, Bayer Animal Health).

Ancylostoma ceylanicum is a common hookworm of dogs, cats and humans in Asia. More recently, this hookworm was found to infect dogs in Australia. The objective of this study was to determine the efficacy of a spot on combination product containing imidacloprid 10% and moxidectin 2.5% (Advocate/Advantage Multi, Bayer Animal Health) against A. ceylanicum in experimentally infected dogs. Twelve dogs were each subcutaneously injected with 300 infective third-stage larvae of A. ceylanicum. Pups were stratified by egg count and randomly allocated equally into control and treatment groups. The pups in the treatment group were each treated with a spot on combination of 10% (w/v) imidacloprid and 2.5% (w/v) moxidectin, administered topically at the skin surface between the shoulder blades. The dogs in the control group were not treated. Egg counts were performed daily until the end of the study period and compared for the treated and control groups. No eggs were detected in the treated group of pups within 4 days of treatment and faecal samples from this group remained negative throughout the rest of the study, resulting in a treatment efficacy (egg reduction) of 100% (P < 0.0001). The egg counts remained high (4,469 +/- 2,064 eggs per gram, epg) in the untreated control group for the rest of the study period. This study demonstrated that the spot on combination containing imidacloprid 10% and moxidectin 2.5 % (Advocate/Advantage Multi, Bayer Animal Health) given at the recommended dose is highly effective against infection with A. ceylanicum in dogs.

Rapid detection of Dirofilaria immitis in mosquito vectors and dogs using a real-time fluorescence resonance energy transfer PCR and melting curve analysis.

A real-time fluorescence resonance energy transfer (FRET) PCR supplemented with melting curve analysis for the rapid molecular detection of Dirofilaria immitis in mosquito vectors and dog blood samples was developed. This real-time FRET PCR was based on the fluorescence melting curve analysis of a hybrid between an amplicon generated from the D. immitis ribosomal RNA gene sequence and specific fluorophore-labeled probes. The sensitivity, specificity, accuracy, and positive and negative predictive values of this method were all 100%. Besides being highly sensitive and specific, this PCR is fast and offers a high throughput. Therefore it is a suitable and powerful tool for the diagnosis and for epidemiological surveys of canine dirofilariasis as well as for molecular xenomonitoring of D. immitis in mosquito vectors.

Differential detection of Brugia malayi and Brugia pahangi by real-time fluorescence resonance energy transfer PCR and its evaluation for diagnosis of B. pahangi-infected dogs.

A real-time fluorescence resonance energy transfer PCR combined with melting curve analysis was developed for differentiating Brugia malayi and Brugia pahangi DNA in host blood using one set of primers and fluorophore-labeled hybridization probes specific for HhaI repetitive DNA. The differentiation of both species was based on their melting temperatures (Tm). The mean Tm +/- SD of B. malayi and B. pahangi were 56.18+/-0.21 and 52.49+/-0.07, respectively. The method was used for the molecular detection of B. pahangi in infected dog blood samples. The diagnostic sensitivity, specificity, accuracy,and positive and negative predictive values of this method were 100%. The detected mean difference of the Tm might allow the simple discrimination of two related species. This method is fast, sensitive, allows for a high throughput, can be performed on very small volumes, and has potential for diagnosis of B. pahangi-infected dogs in endemic areas as well as for large epidemiological investigations.

Efficacy of a combination product containing pyrantel, febantel and praziquantel (Drontal Plus Flavour, Bayer Animal Health) against experimental infection with the hookworm Ancylostoma ceylanicum in dogs.

Ancylostoma ceylanicum is a common hookworm of dogs, cats and humans in Asia. More recently, this hookworm was found to infect dogs in Australia. The objective of this study was to determine the efficacy of a combination product containing pyrantel, febantel and praziquantel (Drontal) Plus Flavour, Bayer) against A. ceylanicum in experimentally infected dogs. Twelve dogs were each subcutaneously injected with 300 infective third-stage larvae of A. ceylanicum. Pups were stratified by egg count and randomly allocated equally into control and treatment groups. The pups in the treatment group were treated orally at 20 days post-infection with a tablet containing pyrantel, febantel and praziquantel (Drontal Plus Flavour, Bayer) with the recommended dose of one tablet per 10 kg bodyweight. The dogs in the control group were not treated. Egg counts were performed daily until the end of the study period and compared for the treated and control groups. No eggs were detected in the treated group of pups within 3 days of treatment, and faecal samples from this group remained negative throughout the rest of the study resulting in a treatment efficacy (egg reduction) of 100% (p = 0.0011). The egg counts for the untreated group remained high for the rest of the study period. This trial demonstrated that a combination tablet containing pyrantel, febantel and praziquantel (Drontal Plus Flavour, Bayer) given at the manufacturer's recommended dose is effective against infection with A. ceylanicum in dogs.

Detection of filarial parasites in domestic cats by PCR-RFLP of ITS1.

Lymphatic filariasis has been targeted by the World Health Organization (WHO) to be eliminated by the year 2020. In addition to chemotherapy and vector control, the control of reservoir hosts is necessary for the control program to succeed. Malayan filariasis, caused by Brugia malayi, is endemic in the South of Thailand where domestic cats serve as the major reservoir host. However, in nature, domestic cats also carry B. pahangi, Dirofilaria immitis and D. repens infections and it is difficult to distinguish the different filarial species from each other just by morphology. To assess the burden of filarial parasites, we performed a study on domestic cats in an endemic area of malayan filariasis in the Prasang district, of Surat Thani, a province in Southern Thailand. Together with Giemsa staining and acid phosphatase activity studies, we performed PCR-RFLP analysis on the first internal transcribed spacer (ITS1) region of ribosomal DNA (rDNA). PCR-RFLP with Ase I could clearly differentiate between B. malayi, B. pahangi, D. immitis and D. repens. Out of the 52 cats studied, filarial parasites were identified in 5 (9.5%) cats, of which 4 (7.6%) were B. pahangi and 1 (1.9%) D. immitis. This PCR-RFLP technique detected two additional cats that were not detected by microscopy. The domestic cats are not an important host of B. malayi in this region. We could develop the PCR-RFLP assay test for differentiating filarial nematodes which can be applied to survey human, animal reservoir hosts and mosquito vectors in endemic areas.

The observation of microfilarial rate and density in cats inoculated with increasing numbers of Brugia pahangi infective larvae.

Having close kinship to Brugia malayi, B. pahangi is a member of the family Filariidae, which causes lymphatic filariasis in dogs and cats. Although this nematode is unlikely to cause a zoonotic disease in humans, study of the B. pahangi life cycle may help control human filariasis. The objective of this study was to examine microfilarial rates and densities of B. pahangi in experimentally induced infections in cats as a relative measurement. Cats were infected with 3 different amounts of 3rd-stage larvae (L3); 100, 300 and 500. Cats infected with 100 L3 became patent for microfilariae longer than the other groups (mean100 = 99+/-44 days). In comparison, the pre-patent period of B. pahangi was somewhat shorter in cats with 300 and 500 L3 infections (mean300 = 76+/-13 and mean500 = 63+/-5 days). The microfilarial densities of these cats were also determined; the density of microfilariae (mf/1 ml blood) increased relative to the duration of infection. One-way ANOVA tests were used to compare the microfilarial densities of the cats with varying numbers of L3. We found that the microfilarial density of cats with 500 L3 exhibited significant differences (p < 0.05) from cats with 300 and 100 L3. However, we concluded that the amount of microfilariae produced in the blood circulation of these cats were not increasing relative to the numbers of L3 taken by the host.