Natural vertical transmission of FIV
S. de Oliveira Medeiros, A. Tanuri, R. Brindeiro
Federal University of Rio de Janeiro, Department of Genetics, Rio de Janeiro, Brazil
Background: Feline immunodeficiency virus (FIV) causes immunodeficiency diseases in cats similar to HIV-1 infected people. Infectious virus is present in saliva, and biting is the major mechanism for spread. Vertical transmission appears to be infrequent in nature. Experimental infection studies have shown that FIV can be passed to kittens during the birth process or via the milk. Here we present a case history giving evidence that the vertical transmission occurred in natural setting.
Methods: A colony of 20 cats, composed mainly by female cats, was observed for five years. The population size is lowering during the years, and one untamed female cat remained alone. This female cat was monitored for three years. During the breeding season two adult male cats were seen in the area. The two males, the queen and two kittens were captured. They were neutered and adopted. Their blood was collected, submitted to DNA extraction and ampliﬁed by nested PCR using primers directed to gag, pol and env regions. The phylogenetic analyses were performed by the neighbor-joining method performed with MEGA 3.1 software. The distance matrix was generated by Kimura´s two-parameter model for nucleotides.
Results: DNA provirus was amplified to the three regions of FIV. By sequence analysis we found that all isolates were of subtype B. The sequence data provided evidence for queen-kitten transmission. Sequences from cats from the same geographic area also were evaluated. Other isolates from the same geographic area have signiﬁcant distinctions. The variability between linked queen-kitten pairs was lower than between unlinked individuals. This suggests that epidemiologically linked sequences were closer to each other evolutionarily than to unlinked sequences.
Conclusions: Our hypothesis is that, as the animals were removed from the original group, the reduced number of males led to an increase in the occurrence of fights over females, thus facilitating the transmission of FIV.
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