Parasitol Res (2013) 112:2393–2395 DOI 10.1007/s00436-013-3311-9
SHORT COMMUNICATION
Indigenous Dirofilaria immitis in Bangladesh Hans-Peter Fuehrer & Moritz Treiber & Katja Silbermayr & Timo A. Baumann & Paul Swoboda & Anja Joachim & Harald Noedl
Received: 30 November 2012 / Accepted: 18 January 2013 / Published online: 29 January 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract Dirofilaria immitis is a parasite of domestic and wild canids and felids in tropical, subtropical and temperate regions throughout the world. The canine heartworm (D. immitis) is the causative agent of canine and feline cardiopulmonary dirofilariasis. This parasite is known to cause a zoonotic disease, namely human pulmonary dirofilariasis. D. immitis is known to be endemic in several South and Southeast Asian countries (e.g. India and Malaysia), but there has previously been no information about the presence of this pathogen in Bangladesh. We present a case of canine dirofilariasis caused by D. immitis in rural southeastern Bangladesh. A male filaroid nematode (95 mm in length and 1.94 mm in width) was identified in the heart of a dog. Species classification was performed by microscopy and molecular tools. Sequence analysis revealed a 100 % identity within the mitochondrial cytochrome c oxidase I (CO1) gene to two Chinese and one Australian D. immitis samples. Usually, dogs stay outside overnight with a high risk to get infected with D. immitis via nocturnal mosquito vectors, which may lead to high prevalences of this pathogen in the canine population and thus increase the risk of human infections with this neglected parasitic disease.
H.-P. Fuehrer (*) : K. Silbermayr : T. A. Baumann : A. Joachim Department of Pathobiology, Institute of Parasitology, University of Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria e-mail:
[email protected] H.-P. Fuehrer : M. Treiber : T. A. Baumann : P. Swoboda : H. Noedl MARIB, Malaria Research Initiative Bandarban, Bandarban, Bangladesh H.-P. Fuehrer : M. Treiber : P. Swoboda : H. Noedl Institute of Specific Prophylaxis and Tropical Medicine, Medical University of Vienna, Vienna, Austria
Seven species of the genus Dirofilaria are currently known to cause zoonotic infections, Dirofilaria immitis (Canidae and Felidae as final hosts), Dirofilaria repens (Canidae), candidatus Dirofilaria hongkongensis (Canidae), Dirofilaria tenuis (Procionydae: racoons), Dirofilaria ursi (Ursidae: bears), Dirofilaria subdermata (Hystricomorpha: porcupines) and Dirofilaria striata (Felidae: bobcats) (To et al. 2012). Among these, the canine filarial species are known to have poor mammalian host specificity (D. immitis and D. repens). Both species are known as zoonotic pathogens, inducing human subcutaneous (D. repens), ocular (D. repens) and pulmonary dirofilariasis (D. immitis), with D. repens as the main causative of human dirofilariasis. The canine heartworm D. immitis is the main cause of canine and feline cardiopulmonary dirofilariasis, whereas humans are not eminently suitable hosts for D. immitis. Although immature D. immitis may invade the human pulmonary artery, the human immune system routinely destroys the worm, resulting in characteristic pulmonary granulomas (human pulmonary dirofilariasis), which on X-rays can be mistaken for pulmonary cancer (Simón et al. 2012). So far, more than 1,700 human cases of dirofilariasis (including >370 pulmonary cases) have been documented worldwide, suggesting that wherever canine dirofilariasis is present humans are at risk of infection (Montoya-Alonso et al. 2010; Simón et al. 2012). D. immitis is transmitted by culicid mosquito vectors (Culex, Aedes, Anopheles and Culiseta) (Simón et al. 2012; Morchón et al. 2012). During the blood meal on an infected host, microfilariae are ingested by mosquitoes. The main final hosts are wild and domestic dogs (Canis lupus familaris) where microfilariae can be found in the blood. D. immitis has also been reported in felids (e.g. tigers) but the low microfilaraemia indicates that feline hosts play no significant role in the transmission of this parasite. D. immitis has been reported in various Asian countries with prevalences in dogs of up to 70 % in some areas of
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Malaysia. In South Asia, information about this pathogen is limited. Both D. immitis and D. repens are known to be endemic in India, Sri Lanka and Iran (Megat Abd Rani et al. 2010; Poppert et al. 2009; Simón et al. 2012). In areas of Bangladesh where dog meat is frequently consumed, the presence of worms in dog hearts has repeatedly been reported by indigenous populations. However, so far, the presence of D. immitis in Bangladesh had not been published. To investigate this “rural legend”, tribal Bawn people provided three fresh dog hearts. The samples were examined and identified as dog hearts by anatomy. The hearts were stored at −20 °C at the Malaria Research Initiative Bandarban field site in Bandarban, Bangladesh. The district of Bandarban is located in the Chittagong Hill Tracts (CHTs), in the very southeast of Bangladesh bordering to Myanmar. In contrast to the primarily Muslim rest of Bangladesh, the CHTs are home to more than ten indigenous groups with different religious backgrounds, some of whom (e.g. Bawn) regularly consume pork, dog and rodent meat (Fuehrer et al. 2012). The hearts were dissected, and in one of them, a worm was found in the right ventricle. By microscopic analysis, it was identified as a male filaroid nematode, measuring 95 mm in length and 1.94 mm in width. For species classification DNA was isolated using a DNeasy Blood and Tissue Kit (Qiagen, Hilden, Germany). Molecular identification was conducted using primers (COIint-F/COIint-R) for amplification of a 667-bp fragment of the mitochondrial cytochrome c oxidase I (CO1) gene as reported previously (Casiraghi et al. 2001). The 25-μl reaction mixtures included 2 μl DNA, 1× BioTaq Buffer, 1 μM of each primer, 2.5 mM MgCl2, 0.2 mM dNTPs and 1 U BioTaq Polymerase (Bioline, Luckenwalde, Germany). DNA was initially denatured at 95 °C for 2 min, followed by 37 cycles of amplification (annealing at 52.3 °C for 30 s, extension at 72 °C for 45 s, denaturation at 95 °C for 30 s) and a final extension of 72 °C for 5 min. Known positive and negative controls were run with the PCR amplification. PCR products were analysed by gel electrophoresis with 2 % agarose and ethidium bromide staining. The PCR product was purified with Illustra™ ExoStar™ 1-Step (GE Healthcare, Buckinghamshire, UK) and sequenced by Sanger Cycle Sequencing (Microsynth, Balgach, Switzerland). Sequence analysis (GenBank® accession number: KC107805) revealed a 100 % identity within the mitochondrial CO1 gene to two Chinese (EU159111, EU163945) and one Australian (AJ537512) D. immitis samples (Hu et al. 2003; Huang et al. 2009). In Bangladesh, putative wild canid hosts (e.g. dhole, red fox, bengal fox) and insect hosts (e.g. Aedes albopictus) are known to be endemic (Ahmed 1987). The rural district of Bandarban is one of the economically weakest regions of Bangladesh and people live under poor housing and hygienic conditions in close contact to domestic animals and pests (Fuehrer et al. 2012). Dogs usually remain outside overnight
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with a high risk of getting infected with D. immitis via nocturnal mosquito vectors, which may lead to high prevalences of this pathogen in the canine population and thus increase the risk of human infections with this neglected parasitic disease. In cases of pulmonary disease in humans, erroneous infections with D. immitis should be included in the differential diagnosis whenever interpreting pulmonary masses in endemic regions. To examine the role and distribution of D. immits and other Dirofilaria species in Bangladesh, further studies of dogs (e.g. in vivo: detection of circulating microfilariae, full dog examination, serology) and culicid vectors are needed as conducted in several other countries previously (e.g. Bargues et al. 2006; Montoya et al. 2006; Rapti and Rehbein 2010; Vezzani et al. 2011). Acknowledgments We wish to thank the tribal Bawn and Marma communities in Bandarban District for providing the samples. Furthermore, we wish to thank Barbara Eigner and Walpurga Wille-Piazzai for the excellent technical assistance. This project was supported by the Malaria Research Initiative Bandarban. Conflict of interest The authors declare that they have no conflict of interest.
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