Jaagsiekte Sheep Retrovirus Can Reach Peyer’s Patches and Mesenteric Lymph Nodes of Lambs Nursed by Infected Mothers

Abstract

Ovine pulmonary adenocarcinoma (OPA) is a contagious lung cancer of sheep caused by jaagsiekte sheep retrovirus (JSRV). It is generally accepted that transmission by the respiratory route occurs under natural conditions. However recent studies strongly indicate that JSRV can also be transmitted to lambs perinatally via colostrum and milk (C/M). The aim of this work was to confirm that C/M can transmit JSRV infection to lambs under natural conditions and investigate the initial events associated with this transmission route. We have analyzed the presence of JSRV in C/M samples from 22 naturally infected, asymptomatic ewes throughout a lactation period, and in various tissues collected from a group of 36 of their lambs that were fed naturally. The lambs were euthanized at 12, 24, 48, and 72 hours and at 5 and 10 days after birth. We detected JSRV-provirus by PCR in the somatic C/M cells from 10/22 ewes (45.45%). The virus was also detected in 9/36 lambs (25%). JSRV-infected cells, with lymphoreticular-like morphology, were observed by immunohistochemistry (IHC) and in situ hybridization (ISH) in Peyer's patches (PP) from the small intestine of the youngest lambs and in mesenteric lymph nodes (MLN) from lambs older than 72 hours. The virus was also detected by PCR in white blood cells (WBC) in 2/36 lambs (5.5%). These results confirm colostral transmission of JSRV to lambs under natural conditions. Infected lymphoreticular cells contained in C/M appear to be involved. These cells can cross the intestinal barrier of newborn lambs, reach the MLN and enter into circulation.

The Diagnostic Challenges of Ovine Pulmonary Adenocarcinoma

“…In lambs younger than six months, progression is usually acute and death occurs within a few days. In adult sheep, the disease progresses more slowly, with clinical signs extending over several weeks or months, until the animal dies [22,30,31].…”

“…Since then, it has been possible to detect the JSRV in asymptomatic animals, and an elevated prevalence has been seen in infected flocks, much higher than the number of animals that further develop the neoplasia [32,73]. The virus can enter into circulation when infected lymphoreticular cells contained in colostrum and milk can pass through the intestinal barrier and arrive to mesenteric lymph nodes [30].…”

“…JSRV has been found in macrophages of infected mother's milk and has been shown to cross the gut barrier of newborn lambs and spread from mesenteric lymphodes and Peyer's Patch. The transplacental pathway does not appear to have any epidemiological significance [28][29][30][31].…”

Jaagsiekte sheep retrovirus found in milk macrophages but not in milk lymphocytes or mammary gland epithelia of naturally infected sheep

“…2,4,6,9,11,14 In addition, JSRV proviral DNA can be detected in somatic cells (SCs) from colostrum and milk (C/M) in sheep in OPA-affected flocks. 3,10 It has also been reported that lambs artificially fed C/M from JSRV-infected ewes became blood-infected at a very early age, 10 and that JSRV can reach Peyer patches and mesenteric lymph nodes of newborn lambs nursed by infected mothers. 3 These data demonstrate that JSRV can be transmitted to lambs through the maternal route via infected C/M, but other details of this means of transmission for JSRV are not known.…”

Exogenous Small Ruminant Betaretrovirus Envelope Protein Is Detected in Draining Lymph Nodes in Contagious Respiratory Tumors of Sheep and Goats

“…14,19 The pathology, epidemiology, transmission, genetic resistance, and ante-mortem tests of the associated diseases have been reported. 1,2, 5,7,16,28 Despite these achievements, information regarding the interactions of these viruses with the immune system still very limited.…”