The comparison of spatial variation and risk factors between mosquito-borne and tick-borne diseases: Seroepidemiology of Ehrlichia canis, Anaplasma species, and Dirofilaria immitis in dogs

Emerging risk of Dirofilaria spp. infection in shelter dogs in southern Italy

In southern Italy, the number of autochthonous cases of Dirofilaria immitis in dogs has increased considerably. This also occurs in the Campania region, particularly in coastal areas, where infections with D. immitis and Dirofilaria repens have been reported more frequently. Therefore the aim of the present study was to better investigate the occurrence of Dirofilaria spp. in a local dog shelter in Castel Volturno (Campania region, southern Italy). Briefly, a total of 260 blood samples were analysed for identification of microfilariae (mff) and detection of Dirofilaria immitis antigen. Dogs were classified according to their age (1-3  years; 4-6  years; 7-11  years; > 11  years) and length of stay in the shelter at the time of sampling (dogs that entered in the shelter in the last 4  months; dogs housed in the shelter for more than 4 months up to 2  years; dogs housed for more than 2  years). The modified Knott's test revealed that 195 dogs (75.0%) were positive for circulating mff of Dirofilaria spp. Specifically, 104/260 (40.0%) dogs were positive for D. immitis and 91/260 (35.0%) were positive for D. repens. In addition, 72/260 (27.7%) dogs had both D. immitis and D. repens mff. Antigen testing revealed that 78/260 (30.0%) dogs were positive for D. immitis. However, 26/104 (25.0%) of the dogs with D. immitis mff were antigen-negative. The overall k concordance between the modified Knott's test and the antigenic test was ≤0.2 (poor) (p = 0.000). The results of the logistic regression model showed a significant association between Dirofilaria exposure and the period of time the dogs had spent in the shelter at the time of sampling. Dogs housed in the shelter for 4 months (group 1) and between 4 months and 2 years (group 2) had higher Dirofilaria positivity than dogs in group 3 (housed for more than 2 years) (80.4% vs. 79.6% vs. 62.4%, respectively). Moreover, male dogs and older dogs (between 7 and 11 years of age) were more likely to be infected with Dirofilaria spp.

The prevalence of canine dirofilariasis in China: a systematic review and meta-analysis

BACKGROUND

Dirofilariasis, the disease caused by Dirofilaria spp., and in particular by Dirofilaria immitis and Dirofilaria repens in canines, occurs frequently in canids and felids, and occasionally in humans, in temperate, sub-tropical and tropical regions globally. Although highly effective, safe and convenient preventive medicines have been available for the treatment of dirofilariasis for the past three decades, the disease remains a major veterinary and public health concern in endemic areas. The insect vectors, host-parasite relationships and interactions of Dirofilaria spp. have received little attention in China, and there is very little information in English regarding the prevalence of dirofilariasis in animals and humans in the country. The aim of this systematic review and meta-analysis is to evaluate the status of canine dirofilariasis in China based on the available literature in English and in Chinese.

METHODS

We systematically searched five databases for epidemiologic studies on the prevalence of canine dirofilariasis in China and finally selected 42 studies eligible for inclusion in the systematic review and meta-analysis. The meta-analysis was performed using the random effects model in the meta package in R v4.2.1.

RESULTS

The random effects model gave a pooled and weighted prevalence of Dirofilaria infection among dogs in China in the past 100 years of 13.8% (2896/51,313, 95% confidence interval 8.2-20.4%) with a high level of heterogeneity (I² =  99.5%).

CONCLUSIONS

Our analyses indicated that the prevalence of canine dirofilariasis in China has gradually declined, but that the range of Dirofilaria spp. has expanded. Older and outdoor dogs presented a higher rate of positive infection. The findings indicated that more attention should be paid to host factors for the effective control and management of this disease.

Ehrlichiosis in Dogs: A Comprehensive Review about the Pathogen and Its Vectors with Emphasis on South and East Asian Countries

Ehrlichiosis in dogs is an emerging vector borne rickettsial zoonotic disease of worldwide distribution. In general, three Ehrlichial species (Ehrlichia canis, E. ewingii, and E. chaffeensis) are involved in infecting dogs. Among them, E. canis is the well-known etiological pathogen affecting platelets, monocytes, and granulocytes. Dogs act as a reservoir, while the main vector responsible for disease transmission is Rhipicephalus sanguineus. However, in east Asian countries, Haemaphysalis longicornis is considered the principal vector for disease transmission. This disease affects multiple organs and systems and has three clinical manifestations, including acute, subclinical, and chronic. Definitive diagnosis involves visualization of morulae on cytology, detection of antibodies through an indirect immunofluorescence test (IFAT), and DNA amplification by polymerase chain reaction (PCR). In canine ehrlichiosis, no predilection of age or sex is observed; however, Siberian Huskies and German Shepherds are more likely to develop severe clinical manifestations. Doxycycline, rifampicin, and minocycline are proven to be effective drugs against canine ehrlichiosis. This review is intended to describe a brief overview of Ehrlichia infection in dogs, its reported prevalence in east and south Asian countries, and the latest knowledge regarding chemotherapy and associated vectors responsible for the disease transmission. This manuscript also identifies the prevailing knowledge gaps which merit further attention by the scientific community.

Dirofilariosis caused by Dirofilaria immitis in the south of Kerman province, Iran

BACKGROUND

Dirofilariosis due to Dirofilaria immitis is endemic in various areas of Iran. Domestic dogs are the main reservoirs and represent a major potential infection source for the vector and humans.

OBJECTIVE

This study aimed to explore the prevalence of dirofilariosis due to D.immitis and its public health importance in domestic dogs in the Jiroft district, south of Kerman province, Iran, by serological and parasitological methods.

METHODS

This descriptive study was carried out as a cross-sectional investigation. A questionnaire was completed for 100 domestic dogs from May 2017 to February 2018 and recorded their age, sex, and clinical features. Also, we used enzyme-linked immunosorbent assay (ELISA) to identify antigens of heartworms in the bloodstream, with 98% sensitivity and 100% specificity, and parasitological techniques (Knott's test) to detect microfilariae in canine blood in Jiroft district, south of Kerman province, Iran.

RESULTS

Overall, 10 (10%) and 4 (4%) domestic dogs were infected as confirmed by ELISA and modified Knott's tests, respectively. The rate of occult infections in the ELISA test than Knott's test was 60%. No significant difference was found between dirofilariosis and gender. In contrast, there was a significant difference between dirofilariosis infection and age (P < 0.05).

CONCLUSION

The present findings could help understand the epidemiological aspects of D. immitis for future control programs and take appropriate preventive and therapeutic strategies against the disease.

Seroprevalence and associated risk factors for vector-borne pathogens in dogs from Egypt

Background

Dogs play an important role as reservoirs of many zoonotic vector-borne pathogens worldwide, yet reports of canine vector-borne diseases (CVBDs) in Egypt are scarce.

Methods

Serum samples were collected from pet dogs (n = 500) of the three most common breeds (German Shepherd, Rottweiler and Pit Bull) in five Governates of Cairo (n = 230), Giza (n = 110), Al-Qalyubia (n = 60), Al-Gharbia (n = 60) and Kafr El-Sheikh (n = 40) with a hot desert climate. The presence of antibodies to Anaplasma spp. (A. phagocytophilum, A. platys), Ehrlichia spp. (E. canis, E. chaffeensis, E. ewingii), Borrelia burgdorferi (s.l.) and Dirofilaria immitis were assessed using IDEXX SNAP^® 4Dx^® ELISA tests. For each pathogen, risk factors (i.e. geographical area, keeping condition, sex, age, breed, tick infestation, weekly sanitation of dog enclosures and application of ectoparasiticides) were evaluated by logistic regression approach.

Results

In total, 18.2% (n = 91, 95% CI 15.1–21.8) of dogs scored seropositive for at least one pathogen, the most frequent being Ehrlichia spp. (n = 56; 11.2%; 95% CI 8.7–14.3) followed by Anaplasma spp. (n = 33; 6.6%, 95% CI 4.7–9.1), Borrelia burgdorferi (s.l.) (n = 9; 1.8%, 95% CI 0.9–3.4) and D. immitis (n = 7; 1.4%, 95% CI 0.9–2.9). In the tested population, 15.4% (95% CI 12.5–18.8) of dogs were exposed to a single pathogen while 2.4 (95% CI 1.4–4.2) and 0.4% (95% CI 0.1–1.4) were simultaneously exposed to two or three pathogens, respectively. Major risk factors associated with VBDs were living outdoors (Anaplasma spp., P = 0.0001; Ehrlichia spp., P = 0.0001), female sex (Ehrlichia spp., P = 0.005), German Shepherd breed (Anaplasma spp., P = 0.04; Ehrlichia spp., P = 0.03), tick infestation (Anaplasma spp., P = 0.0001; Ehrlichia spp., P = 0.0001; B. burgdorferi (s.l.), P = 0.003; D. immitis, P = 0.02), irregular sanitation (Anaplasma spp., P = 0.0001; Ehrlichia spp., P = 0.0001; B. burgdorferi (s.l.), P = 0.002; D. immitis, P = 0.01) and not using ectoparasiticides (Anaplasma spp., P = 0.0001; Ehrlichia spp., P = 0.0001; B. burgdorferi (s.l.), P = 0.007).

Conclusion

To our knowledge, this is the first large-scale seroepidemiological study of CVBDs in Egypt. Considering that all of the detected pathogens are potentially zoonotic, effective ectoparasite control strategies, regular examination of pet dogs and successful chemoprophylaxis are advocated.

Molecular Survey of Vector-Borne Pathogens of Dogs and Cats in Two Regions of Saudi Arabia

Dogs and cats play an important role as reservoirs of vector-borne pathogens, yet reports of canine and feline vector-borne diseases in Saudi Arabia are scarce. Blood samples were collected from 188 free-roaming dogs and cats in Asir (70 dogs and 44 cats) and Riyadh (74 dogs), Saudi Arabia. The presence of Anaplasma spp., Bartonella spp., hemotropic Mycoplasma spp., Babesia spp., and Hepatozoon spp. was detected using a multiplex tandem real-time PCR. PCR-positive samples were further examined with specific conventional and real-time PCR followed by sequencing. Dogs from Riyadh tested negative for all pathogens, while 46 out of 70 dogs (65.7%) and 17 out of 44 cats (38.6%) from Asir were positive for at least one pathogen. Positive dogs were infected with Anaplasma platys (57.1%), Babesia vogeli (30%), Mycoplasma haemocanis (15.7%), and Bartonella henselae (1.4%), and cats were infected with Mycoplasma haemofelis (13.6%), Candidatus Mycoplasma haemominutum (13.6%), B. henselae (9.2%), and A. platys (2.27%), all of which are reported for the first time in Saudi Arabia. Co-infection with A. platys and B. vogeli was detected in 17 dogs (24.28%), while coinfections were not detected in cats. These results suggest that effective control and public awareness strategies for minimizing infection in animals are necessary.

An analysis of time trends for canine heartworm disease in Grenada and its associated risk factors based on veterinary clinical pathology laboratory data base records between 2003 and 2015

Canine heartworm (CHW) disease is a common parasitic infection in dogs in the Caribbean islands. However, studies on temporal trends and risk factors are limited for this region. This study represents the time trends in laboratory prevalence and risk factors of canine heartworm infections between 2003 and 2015. In this case series, 662 cases of laboratory-diagnosed heartworm were compared to 662 dogs without a laboratory diagnosis of heartworm (controls). One hundred and seventy two frozen serum positive samples were later analyzed for heartworm antigens using Heska solo® Step CH, and all 172 cases of microfilariae were confirmed as Dirofilaria immitis. Annual prevalence, linear trends and odds ratios (OR) for CHW were estimated using EPIINFO version 7 at a significance level of α = 0.05. Logistic regression was used to assess the association of CHW with variables showing a statistically significant univariate relationship. Laboratory prevalence of CHW decreased from 72 cases per 1000 dogs per year in 2003 to 15 cases per 1000 dogs per year in 2015 [X² for linear trend = 151.8, p < 0.0001], with the occurrence of an epidemic of CHW between 2008 and 2010. The odds of CHW were higher among adult dogs [(OR) = 3.9 (95% CI, 2.9-7.0)] and geriatric dogs [OR = 2.1 (95% CI, 1.1-4.3)] compared to puppies. The odds of CHW were higher [OR = 1.3 (95% CI, 1.1-1.6)] among male dogs than female dogs, but the odds for CHW were lower among neutered dogs [OR = 0.4 (95% CI, 0.2 - 0.6)] compared to intact dogs. The odds of a dog being diagnosed with CHW were elevated [OR = 4.1 (95% CI, 3.2-5.2)] during the dry season compared to the rainy season. Our findings show that canine heartworm is extensive in laboratory submissions in Grenada. However, the laboratory prevalence of CHW decreased between 2003 and 2015, with an epidemic occurring between 2008 and 2010. Age of the dog, sex, neutered status, and seasonality of diagnosis were significantly associated CHW in Grenada.

The global status of Dirofilaria immitis in dogs: a systematic review and meta-analysis based on published articles

Dirofilaria immitis is a parasitic filarial nematode responsible for heartworm disease in domestic as well as wild canines and felines and pulmonary or cutaneous infections in humans. This systematic review and meta-analysis aimed to evaluate the status of D. immitis in dogs based on available literature. Four English language databases (ISI Web of Science, Scopus, PubMed and Science Direct) containing data on D. immitis prevalence in dogs were thoroughly searched resulting in the inclusion of 193 studies. The findings revealed that the pooled and weighted prevalence of D. immitis infection in dog population based on published papers throughout the world was 10.91% (95% CI=10.18-11.65). In addition, subgroup analysis based on meta-regression revealed that a significant difference between the pooled and weighted prevalence of D. immitis in dogs and country (β =0.14, P=0.049). Given the relatively high prevalence of D. immitis infection in dogs and its adverse effects, it is suggested that to perform more research on the prevention and control of dirofilariasis infection in dogs worldwide.

Seroprevalence of Dirofilaria immitis in Cats from Liaoning Province, Northeastern China

The present study was performed to investigate the seroprevalence and risk factors for Dirofilaria immitis infection in cats from Liaoning province, northeastern China. From October 2014 to September 2016, sera of 651 cats, including 364 domestic cats and 287 feral cats (332 females and 319 males) were assessed. They were tested for the presence of D. immitis antigen using SNAP Heartworm RT test kit. In this population, the average prevalence was 4.5%. Age and rearing conditions (feral or domestic) were found to be associated with the prevalence of D. immitis. The prevalence was significantly higher in feral cats compared with domestic cats (8.4% vs 1.4%, P<0.01). There was no significant difference between males and females (4.7% vs 4.2%, P>0.05), but older cats (≥3 years old) showed a statistically higher prevalence compared with younger cats (<3 years old) in feral populations (16.8 vs 2.4%, P<0.01), while the difference between the age groups was not statistically significant in domestic cats (2.4% vs 0.51%, P>0.05), all these results suggest that outdoor exposure time may be one of the most important factors for D. immitis prevalence in cats. Results reveal that D. immitis are prevalence in domestic and feral cats in northeastern China, which indicates that appropriate preventive measures should be taken to decrease the incidence of feline heartworm disease in Liaoning province, northeastern China.

The prevalence of Anaplasma platys and a potential novel Anaplasma species exceed that of Ehrlichia canis in asymptomatic dogs and Rhipicephalus sanguineus in Taiwan

Canine anaplasmosis is regarded as an infection by Anaplasma platys rather than zoonotic Anaplasma phagocytophilum in subtropical areas based on the assumption that the common dog tick species is Rhipicephalus sanguineus, which transmits E. canis and presumably A. platys. We investigated asymptomatic dogs and dog ticks from 16 communities in Nantou County, Taiwan to identify common dog tick species and to determine the prevalence of Anaplasma and Ehrlichia spp. Of total 175 canine blood samples and 315 ticks, including 306 R. sanguineus and 9 Haemaphysalis hystricis, 15 dogs and 3 R. sanguineus ticks were positive for E. canis, while 47 dogs and 71 R. sanguineus ticks were positive for A. platys, via nested PCR for 16S rDNA and DNA sequencing of selected positive amplicons. However, among the dogs and ticks that were positive to A. platys 16S rDNA, only 20 dogs and 11 ticks were positive to nested PCR for A. platys groEL gene. These results revealed the importance of searching for novel Anaplasma spp. closely related to A. platys in dogs and ticks. Seropositivity to a commercial immunochromatographic test SNAP 4Dx Anaplasma sp. was not significantly associated with PCR positivity for A. platys but with infestation by ticks carrying A. platys (P<0.05). Accordingly, R. sanguineus may be involved in transmission of A. platys but may not act as a reservoir of E. canis and PCR results for 16S rDNA could be a problematic diagnostic index for A. platys infection.

Prevalence of antibodies against Ehrlichia spp. and Orientia tsutsugamushi in small mammals around harbors in Taiwan

BACKGROUND

Tick-borne ehrlichiosis and mite-borne scrub typhus represent important emerging zoonotic rickettsial diseases. Although scrub typhus has been recognized by the Taiwanese public health system, information on ehrlichial infections is scarce in Taiwan. In this study, the risk of spread of ectoparasites on rodents through aerial and marine transportation was assessed in international and domestic harbors. Here, we report the first systematic surveillance of seroprevalence against Ehrlichia spp. in small mammals on the main island of Taiwan.

METHODS

In total, 1648 small mammals were trapped from 8 international ports, 18 domestic fishing harbors, and 7 local public health centers around Taiwan from November 2004 to December 2008. Sera were analyzed using indirect immunofluorescence assays to detect IgG antibodies against Ehrlichia chaffeensis and Orientia tsutsugamushi. A serum titer of ≧1:80 was considered positive.

RESULTS

Antibodies against Ehrlichia spp. and O. tsutsugamushi were detected in 3.28% and 4.92% of small mammals active around harbors, respectively. The seropositive rate against Ehrlichia was higher in northern Taiwan from 2005 to 2008. However, O. tsutsugamushi infections increased in southern Taiwan during this period. The serological evidence of ehrlichial and O. tsutsugamushi infections in all international ports were included in the study. No significant differences were found among the seropositive rates of Ehrlichia spp. and O. tsutsugamushi in small mammals trapped between international and local harbors.

CONCLUSIONS

The overall prevalence of Ehrlichia spp. and O. tsutsugamushi infections in small mammals active around harbors was 3.28% and 4.92%, respectively. The results provided serological evidence supporting the potential risks of transporting pathogens through air and maritime traffic. This study highlights serious issues of the emergence and spread of rickettsial diseases in Taiwan. The incidence of human ehrlichiosis requires further investigation.

Prevalence of select vector-borne pathogens in stray and client-owned dogs from Algiers

Data on the prevalence of vector-borne diseases agents infecting canines in Algeria is currently lacking. The purpose of this study is to assess by serological and molecular methods the prevalence of select arthropod borne-bacterial infections in client-owned and stray dogs. Antibodies to Anaplasma phagocytophilum were the most prevalent at 47.7%, followed by Borrelia burgdorferi s.l. at 37.6%, Ehrlichia canis at 30.0%, Bartonella henselae at 32.4% and Bartonella vinsonii subsp. berkhoffii at 27%. Seroprevalence was statistically significantly higher in stray dogs than those owned by clients. Seropositivity was not associated with health status, except for E. canis. Molecular evaluation indicates that 17.8% of the 213 analyzed dogs were positive for Ehrlichia and Anaplasma with a prevalence of 4.2% for E. canis, 14.1% for Anaplama platys and 0% for A. phagocytophilum. Seven (7.1%) of the tested dogs were positive for Bartonella spp. with two characterized as Bartonella rochalimae, four as B. henselae and one as B.v. subsp. berkhoffii.

Prevalence of canine heartworm (Dirofilaria immitis) disease in dogs of central Portugal

The aim of the present study was to determine the prevalence and risk factors concerning Dirofilaria immitis infection in dogs from Figueira da Foz, located in the central region of Portugal. In the period between November 2009 and January 2011, 304 blood samples were obtained from dogs over 1 year of age, with no previous history of heartworm prevention or diagnosis. Every blood sample was analyzed using varied laboratory techniques (direct microscopic evaluation of a fresh blood sample, the modified Knott technique, and the ELISA antigen detection test - IDEXX Snapp®). In the samples in which microfilaremia was detected, a histochemical technique using acid phosphatase staining was applied to identify the species of microfilariae. A total prevalence of 27.3% (83 out of 304) was found. We also found that 73.5% of all positive cases (61 out of 83) were microfilaremic, and 26.5% were occult infections (22 out of 83). By means of a histochemical technique Dirofilaria immitis was identified in 96.7% of microfilaremic samples. A multivariate model allowed us to identify the following risk factors for the presence of heartworm disease: age between 4 and 9 years, dogs living in a rural environment, large breed dogs, and living outdoors. This study shows for the first time the high prevalence of heartworm disease in a central area of Portugal and emphasizes the importance of systematic screening for this disease, as well as the need to prevent it in dogs in this area.

Vector-borne pathogens in dogs from Costa Rica: first molecular description of Babesia vogeli and Hepatozoon canis infections with a high prevalence of monocytic ehrlichiosis and the manifestations of co-infection

Infection with canine vector-borne pathogens was evaluated in dogs from four different regions of Costa Rica by PCR. Demographic data, clinical signs, packed cell volume values, and the presence of tick infestation were recorded for each dog. Forty seven percent (69/146) of the dogs were infected with at least one pathogen and 12% were co-infected with two pathogens. Ehrlichia canis was detected in 34%, Anaplasma platys in 10%, Babesia vogeli in 8%, and Hepatozoon canis in 7.5% of the blood samples. No infection was detected with Leishmania spp. in blood, skin scrapings or conjunctival swabs. Thirty percent of the dogs presented at least one clinical sign compatible with vector-borne disease, and of those, 66% were infected with a pathogen. Subclinical infections were determined in 58% of the infected dogs including 82% (9/11), 58% (29/50), 42% (5/12) and 36% (5/14) of the dogs with H. canis, E. canis, B. vogeli and A. platys infections, respectively. A distinct relationship was found between infection and anemia. The mean PCV values were 34.4% in dogs with no infection, 31.5% in those who had a single infection and 23% in those with co-infection. Co-infected dogs had significantly lower PCV values compared to non-infected and single-infected dogs (p<0.0001). Thirty five percent (51/146) of the dogs were infested with ticks, 82% of them were infested with Rhipicephalus sanguineus sensu lato and 18% with Amblyomma ovale. Dogs infected with A. platys, B. vogeli, or E. canis were significantly associated with R. sanguineus s.l. infestation (p<0.029). This is the first description of infections with B. vogeli and H. canis in Costa Rica as well as in Central America. The results of this study indicate that multiple vector-borne pathogens responsible for severe diseases infect dogs in Costa Rica and therefore, increased owner and veterinarian awareness are needed. Moreover, prevention of tick infestation is recommended to decrease the threat of these diseases to the canine population.