Avian and human influenza A virus receptors in trachea and lung of animals.

Background: Influenza A viruses are capable of crossing the specific barrier between human beings and animals resulting in interspecies transmission. The important factor of potential infectivity of influenza A viruses is the suitability of the receptor binding site of the host and viruses. The affinities of avian and human influenza virus to bind with the receptors and the distributions of receptors in animals are different. Objective: This study aims to investigate the anatomical distribution of avian and human influenza virus receptors using the double staining lectin histochemistry method. Methods: Double staining of lectin histochemistry was performed to identify both SA α2,3 Gal and SA α2,6 Gal receptors in trachea and lung tissue of dogs, cats, tigers, ferret, pigs, ducks and chickens. Results: We have demonstrated that avian and human influenza virus receptors were abundantly present in trachea, bronchus and bronchiole, but in alveoli of dogs, cats and tigers showed SA α2,6 Gal only. Furthermore, endothelial cells in lung tissues showed presence of SA α2,3 Gal. Conclusion: The positive sites of both receptors in respiratory tract, especially in the trachea, suggest that all mammalian species studied can be infected with avian influenza virus. These findings suggested that dogs and cats in close contact with humans should be of greater concern as an intermediate host for avian influenza A in which there is the potential for viral adaptation and reassortment.

Coinfection of Leptospira spp and Toxoplasma gondii among stray dogs in Bangkok, Thailand.

Leptospirosis and toxoplasmosis are zoonotic diseases with global importance. Asymptomatic animals harboring these pathogens may act as carriers to other animals including humans. The objective of this study was to investigate the seroprevalence of Leptospira and Toxoplasma infections in stray dogs in Bangkok. A total of 230 stray dogs from monasteries in a Bangkok district were examined for specific antibodies to T. gondii and Leptospira. The seroprevalence of T. gondii was determined by a modified latex agglutination test (cut off 1 > or = 64). A microscopic agglutination test was performed to detect antibodies to Leptospira (cut off, 1:100). The seroprevalences of T. gondii and Leptospira were 10.9% (25/ 230) and 83.5% (192/230), respectively. Leptospira serovar bataviae was the most predominant (20.3%) serovar. Co-infection with Leptospira and Toxoplasma was found in 22 dogs (9.6%). The prevalence of Toxoplasma in females was significantly higher than in males (p < 0.05), but no significant differences was observed for Leptospira. The high seroprevalence of these two diseases in dogs is of public health concern because close contact between dogs and humans may provide a link between a reservoir in the environment and susceptible humans.