Abstract
This study aimed to evaluate by means of Nested Polymerase Chain Reaction (nPCR), co-cultivation and sequencing, with genetic comparison between strains (mother/newborn), the occurrence of vertical transmission of Small Ruminant Lentiviruses (SRLV) from naturally occurring nannies infected for their offspring. For the detection of SRLV seropositive progenitors, blood was collected from 42 nannies in the final third of gestation in tubes with and without anticoagulant. The diagnostic tests used were Western Blot (WB) and nPCR. During the period of birth, the same blood collection procedure was performed on 73 newborns at zero hours of birth, with the same diagnostic tests. Seventeen blood samples from seven-day-old kids, proven positive for SRLV by nPCR, chosen at random, were subjected to coculture in goat synovial membrane (GSM) cells for 105 days. The pro-viral DNA extracted from the cell supernatant from the coculture was subjected to nPCR. For DNA sequencing from the nPCR products, nine positive samples were chosen at random, four nannies with their respective offspring, also positive. Each sample was performed in triplicate, thus generating 27 nPCR products of which only 19 were suitable for analysis. Among the 42 pregnant goats, in 50% (21/42) pro-viral DNA was detected by nPCR, while in the WB, only 7.14% (3/42) presented antibodies against SRLV. Regarding neonates, of the 73 kids, 34 (46.57%) were positive for the virus, using the nPCR technique, while in the serological test (WB), three positive animals (4.10%) were observed. The coculture of the 17 samples with a positive result in the nPCR was confirmed in viral isolation by amplification of the SRLV pro-viral DNA. When aligned, the pro-viral DNA sequences (nannies and their respective offspring) presented homology in relation to the standard strain CAEV Co. It was concluded that the transmission of SRLV through intrauterine route was potentially the source of infection in the newborn goats.
Highlights
Small ruminant lentiviruses (SRLV) are viral agents that affect sheep and goats, and that share homologous sequences in the organization of the genome [1]
It is noteworthy that the herd used for this study has been submitted to a SRLV control program, with the following actions being applied: the semi-annual serological diagnosis of all animals by Western Blot (WB), according to the methodology described in the literature [23]; separation of the mother’s goats soon after birth, without the mother having any contact with them [24] and the supply of colostrum submitted to heating at 56 ̊ C for one hour [25]
When co-culturing samples from 17 neonates with a positive result in the Nested Polymerase Chain Reaction (nPCR), their positivity was confirmed via isolation by amplifying the SRLV pro-viral deoxyribonucleic acid (DNA)
Summary
Small ruminant lentiviruses (SRLV) are viral agents that affect sheep and goats, and that share homologous sequences in the organization of the genome [1]. These viral agents belong to the Retroviridae family, which are able to transcribe ribonucleic acid (RNA) to deoxyribonucleic acid (DNA), through the action of the reverse transcriptase enzyme, and often cross the interspecific barrier between sheep and goats, with great genetic variability [2,3]. The gag gene is one of the most conserved regions of the viral genome [7], and worldwide it is the target of molecular analysis [3,6,8,9,10,11,12], allowing to properly characterize the circulating strains in the infected animal’s organism due to its ideal minimum genetic variability, compared to other conserved regions of the genome [13,14]
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