Brugia spp

From Dog
Adult B. pahangi under light microscopy[1]

Brugia spp are a mosquito-borne haematophagous zoonotic parasite of dogs.

Pathogenic species in dogs include:

  • Brugia malayi
  • Brugia pahangi

The life cycle of this parasite involves transmission of infective L1 larvae by mosquitoes, which subsequently feed on dogs and transmit infective L3 larvae. Adult Brugia spp usually reside in the mandibular, retropharyngeal and axillary lymphatics.

Dual infections with Dirofilaria immitis, Microfilaria auquieri and Acanthocheilonema reconditum are common[2].

An intimate relationship exists between Brugia spp development, reproduction and survival and the endosymbiontic alphaproteobacteria Wolbachia spp, and needs to be understood to understand the etiopathogenesis of this disease in dogs. In filaria, Wolbachia is an obligate mutualistic symbiont that plays an essential role in oogenesis and embryogenesis in adult worms and during larval development[3]. Symptoms of Brugia infection are correlated not so much with adult filariids but with Wolbachia-surface proteins, which induce an inflammatory response associated with the pathogenesis of onchocerciasis through the activation of an innate immune response[4]. Elimination of Wolbachia by antibiotic treatment leads to infertility of the female worms, inhibition of larval molting, and atrophy and death of adult worms (macrofilaricidal effect).

Serological surveys show high prevalence of this parasite in South-East Asia and India[5].

Clinical signs in dogs usually involves lymphadenopathy and lymphedema, but this can be complicated in dogs with co-infections with D. immitis. Limb edema, particularly unilateral hind limb involvement is commonly observed[6][7]. In selective breeding studies with beagles, occult infections appears to be more pathogenic than dogs with microfilaremia, underlying the role genetics play in clinical manifestations with this disease[8].

Diagnosis can be determined using wet smears of fresh blood to detect microfilariae), ELISA assays for detection of antibodies or antigens[9], and PCR for speciation of the parasite[10].

Treatment with doxycycline is relatively effective at eliminating Wolbachia spp which resides in the reproductive tract of brugia[11]. Doxycycline given at 10 mg/kg orally twice daily for 30 days has efficacy against migrating tissue-phase larvae and juvenile worms and will delay or restrict microfilarial production[12].

Adulticidal drugs, primarily moxidectin[13], selamectin, doramectin and ivermectin are larvicidal and sterilize adult filariids and are useful both as preventative and prophylactic drugs.

References

  1. Lincoln. ac.uk
  2. Megat Abd Rani PA et al (2010) A survey of canine filarial diseases of veterinary and public health significance in India. Parasit Vectors 3:30
  3. Ghedin E et al (2009) Brugia malayi gene expression in response to the targeting of the Wolbachia endosymbiont by tetracycline treatment. PLoS Negl Trop Dis 3:e525
  4. Brattig NW et al (2004) The major surface protein of Wolbachia endosymbionts in filarial nematodes elicits immune responses through TLR2 and TLR4. J Immunol 173:437–445
  5. Ambily VR et al (2011) Detection of human filarial parasite Brugia malayi in dogs by histochemical staining and molecular techniques. Vet Parasitol 181(2-4):210-214
  6. Miller S et al (1991) Inhibition of antigen-driven proliferative responses and enhancement of antibody production during infection with Brugia pahangi. J Immunol 147(3):1007-1013
  7. Orton S et al (1998) Association of elevated lymph node cell release of histamine and tumor necrosis factor with genetic predisposition to limb edema formation in dogs infected with Brugia pahangi. Am J Trop Med Hyg 58(6):695-704
  8. Schreuer D & Hammerberg B (1993) Modulation of cellular and humoral immunity, and disease manifestation during onset of patency in Brugia pahangi-infected dogs. Immunology 79(4):658-666
  9. Wongkamchai S et al (2003) An antigen detection assay for diagnosing filariasis. Asian Pac J Allergy Immunol 21(4):241-251
  10. Thanchomnang T et al (2010) 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. Parasitol Res 106(3):621-625
  11. Rossi MI et al (2010) Detection of Wolbachia DNA in blood from dogs infected with Dirofilaria immitis. Exp Parasitol 126(2):270-272
  12. McCall JW et al (2011) Effects of doxycycline on early infections of Dirofilaria immitis in dogs. Vet Parasitol 176(4):361-367
  13. Al-Azzam SI et al (2007) Comparison of the pharmacokinetics of moxidectin and ivermectin after oral administration to beagle dogs. Biopharm Drug Dispos 28(8):431-438