The case was a stray dog found dead with fracture of hip, presumably due to hit by a vehicle. When the dog was necropsied, liver revealed multifocal random small grey white firm foci. Histopathological examination of the foci (855.62µm to 940.60 µm diameter) revealed multiple random large collection of numerous eggs surrounded by mild inflammatory reaction consisting of a few lymphocytes, macrophages and fine fibrosis (Fig. 2). The eggs were numerous and of various sizes, approximately measuring 59.39 x 30.46 µm with characteristic barrel shape, bipolar ends, bilayered wall, cross striations between the walls, condensed or disintegrated yolk. The glycolic wall of the oocysts was distinct pink with PAS (Fig. 3) and brown black with Warthin-Starry stain. Our morphological findings were consistent with earlier reports (Patil et al. 2017; Demirer et al. 2018; de Oliveira et al. 2021). However, no granulomatous or calcified lesions, as reported (Yadav et al. 2016; Ochi et al. 2017; Demirer et al. 2018) was observed. Marked portal to portal fibrosis was demonstrated for collagen by Masson’s trichrome (Fig. 4) and for reticulin by Warthin-Starry stains. Li et al. (2010) had discussed that the inflammatory reaction persist until the worm eggs become encysted or calcified followed by septal fibrosis due to activation of Kupffer cells. Septal fibrosis was evident in intermediate stage of infection and persisted through chronic stage in an experimental infection of C. hepatica in rats (Andrade and Andrade 2004). No adult worm was observed in serial sections in the liver of dog studied. In the life cycle of C. hepaticum, sexually mature female adult worms live for about 40-60 days, lays eggs in liver portal space and then degenerate. Once reproductive function is fulfilled the adult parasite dies and gradually degenerate (Demirer et al. 2018). Hence, the stage of parasitic infection was diagnosed as intermediate to chronic as there was absence of adult worm, encysted ova, minimal inflammation and marked portal fibrosis. The dog could have been infective only on decomposition or predation, as eggs are not passed in feces from liver.
This parasitic infection goes undiagnosed due to nonspecific clinical manifestations in humans and animals. Hepatic biopsy and incidental histopathological findings in liver after death were the commonly reported diagnostic methods although other clinical investigations like ultrasound, serological methods are helpful and mostly followed in humans (Ochi et al., 2017). This parasitic infection must be considered as a disease to be ruled out whenever symptoms or lesions of hepatic abnormalities are encountered.
A seasonal occurrence of hepatic calodiosis in a puppy was reported in spring in Turkey (Demirer et al.,2018). In the present case, the infected stray dog died in October which was a period of monsoon in Tamil Nadu, with rain water stagnation, dead rodent carcasses, lowered temperature, an environmental condition favorable for the embryonation of eggs of C. hepaticum. The stray dog could have contracted the infection up on eating rodent carcass or through contaminated soil or feed with eggs of C. hepaticum and could have become infective if it was just lying on the road without being found, and upon decomposition the dissemination of eggs in soil or by predation could have occurred. C. hepaticum parasitic infection in dogs may pose an increased risk to human health, contribute to the dissemination of eggs if in spurious form of infection from intestine through excrements on streets and serve as a source of infection for other animals (Quadros et al. 2016; Demirer et al. 2018).
Sporadic cases of hepatic capillariasis were reported in humans in India and the reports were mostly among children between 1-5 years with serious liver abnormalities (Nabi et al. 2007; Yadav et al. 2016) due to soil-hand-mouth habit (Misra et al. 2008). Epidemiological studies on prevalence of this parasitic infection is scarce among human and animals. Humans are intercalary or accidental host similar to dogs, hence adequate personal protection while handling of animals/dead or decomposed carcass, safe disposal, avoiding contact with contaminated soil or feces, uncooked meat and proper disinfection of hands of person/fomites/premises is to be adopted.
This paper documents an incidental finding of hepatic calodiosis with cirrhosis in a stray dog. A need to study the prevalence of the disease in human and animals and attempts for early diagnosis is emphasized. A caution in general about the zoonotic threat to children/pet parents/ veterinarians/animal handlers caused by Calodium hepaticum infection which is poorly diagnosed and sporadically reported in India and worldwide.