| dc.description.abstract | Bovine vaccinia (BV) is a zoonotic disease caused by Vaccinia virus (VACV) and affect mainly dairy cows and humans. Previous studies have detect viral viable particles of VACV in milk samples of natural and experimentally infectious cows. But, is unknown if the contaminated milk can transmit VACV after consumption. On the other hand, there is a study that detected neutralizing antibodies (NA) against VACV in humans, including children. These people lived in BV endemic áreas, but they never had contact with sick cows what suggesting that VACV can be transmited by others routes. Thus, it becomes important to study the possible transmission of VACV by milk and detection and viability of the vírus in artisan cheeses. This thesis was divided in four chapters and the aims were to study the transmission of VACV by milk in murine model and detection and viability of poxvirus in artisan cheeses and milk. In the chapter 1, thirty mice were inoculated orally with 100 µl of milk containing 106 PFU of VACV-GP2 (infected group). Oral swab (OS), faeces, blood and tissues samples were collected and analised. The mice showed not clinical signs. Viral DNA was detected, intermittently, in OS from 2nd d.p.i. to 10th d.p.i. while in blood and faeces samples from 5th d.p.i. to 30th d.p.i. At all times, viral DNA was detected in tissues samples, except stomach and duodenum. In immunohistochemistry test was observed intracytoplasmic immunostaining in all tissues, except heart, tonsil, tongue, stomach and duodenum. NA were detected on the 20th and 30th d.p.i. in 50% of mice infected. In the chapter 2, 12 litres of milk were contaminated with 105 PFU/ml of VACV-GP2 and six contaminated cheeses were produced. The cheeses were subjected to the process maturation during 1,7,14,21,45 and 60 days to 25ºC. Real time PCR and titration VERO cells were performed. The viral quantification and titration reduced during the maturation process, but there was not statistical difference. The chapter 3 refers to the detection of VACV in artisan cheeses commercial from properties with and without BV outbreaks. Fifty nine fresh and matured artisan cheeses were collected and analyzed, of which 10 and 49 artisan cheeses were produced in properties with and without BV outbreaks, respectively. PCR-nested technique was perfomed for detection viral DNA. Positive samples were inoculated in VERO cells or chorioallantoic membrane of embryonated chicken eggs and immunoperoxidase in monolayer cell assay (IPMA) and real time PCR were used to confirm the cytopathic effect, respectively. Viral DNA was detected in 43 of 59 samples. These, 11 samples had viral infectious particles, of which four artisan cheeses produced in properties without BV outbreaks. In the last chapter, six dairy properties in Minas Gerais state with outbreaks vesicular diseases in dairy cows, calves and human were visited. Ten dairy cows with lesions in teats were selected, randomly, in each property. Milk and crust samples were collected, totalizing 60 and 12 samples, respectively. These six properties were detected VACV in samples crusts. The coinfection between PPV and VACV was confirm in four properties by convencional PCR for gene B2L amplification. Milk samples were analyzed only the four positive farms for PPV, totalizing 40 samples. PPV DNA was detected in 12 samples, accounting for 30% of samples tested. These 12, eight samples had coinfection between PPV and VACV, accounting for 66,7%. The results showed that contaminated milk can be source of transmission of VACV in murine model and mice infected do not present clinical signs and can eliminate vírus by faeces and oral mucosa. Moreover, the maturation processo is able to reduce viral load in cheeses, but it does not inactived VACV at least 60 days. The detection de VACV in commercial artisan cheeses samples, mainly produced in properties without BV outbreaks, suggest that VACV can circular silently between properties. Futhermore, milk samples can be contaminated with two or more poxvirus species. Thus, the consumption of contaminated milk and artisan cheeses with VACV can be public health risk. But, more studies are necessary to determine the possible risk of vírus transmission to humans associated to consumption of milk and artisan cheeses contaminated with VACV. | |
