Assessment of Stomoxys calcitrans (Diptera: Muscidae) as a vector of porcine reproductive and respiratory syndrome virus

Abstract

Porcine Reproductive and respiratory syndrome (PRRS) is a globally significant swine disease caused by an arterivirus. The virus replicates in alveolar macrophages of infected pigs, resulting in pneumonia in growing pigs and late-term abortions in sows. Outbreaks occur on disparate farms within an area despite biosecurity measures, suggesting mechanical transport by arthropods. We investigated the vector potential of stable flies, Stomoxys calcitrans (L.) (Diptera: Muscidae), in the transmission of porcine reproductive and respiratory syndrome virus (family Arteriviridae, genus Arterivirus, PRRSV) under laboratory conditions. Stable flies were collected around PRRS-negative boar stud barns in North Carolina and tested for presence of the virus. Stable flies were collected on alsynite traps placed near the exhaust fan of the close-sided tunnel-ventilated buildings, suggesting blood seeking flies are attracted by olfactory cues. No flies were positive for PRRSV. We assessed transmission of the virus through an infective bite by feeding laboratory reared stable flies on blood containing virus and transferring them to naive pigs for subsequent bloodmeals. Transmission of the virus to naive pigs by infective bites failed in all attempts. The volume of blood contained within the closed mouthparts of the stable fly seems to be insufficient to deliver an infective dose of the virus. Stable flies are unlikely to transmit PRRSV from one pig to another while blood feeding. The fate of the virus after a bloodmeal remains to be determined.

Rochon K, Baker R B, Almond G W, Watson D W. Assessment of Stomoxys calcitrans (Diptera: Muscidae) as a vector of porcine reproductive and respiratory syndrome virus. Journal of medical entomology 2011;48(4):876-883.

Vet Microbiol. 2011 Jul 1. [Epub ahead of print]

Comparative pathogenicity of type 1 and type 2 isolates of porcine reproductive and respiratory syndrome virus (PRRSV) in a young pig infection model.

Martínez-Lobo FJ, Díez-Fuertes F, Segalés J, García-Artiga C, Simarro I, Castro JM, Prieto C.

Source

Dpto. Sanidad Animal, Facultad de Veterinaria, Universidad Complutense de Madrid, 28040 Madrid, Spain.

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) isolates are classified in two different genotypes, based on genomic heterogeneity: type 1, which comprises European type isolates, and type 2, which includes North American type isolates. It is believed that members of both genotypes differ in some biological properties including pathogenicity, however extensive studies comparing isolates of both genotypes have never been carried out. The objective of the present study was to compare the pathogenic properties of six different PRRSV isolates, three of type 1 and three of type 2, in a young pig infection model. For this purpose, a total of 105 3-week-old piglets were divided in 7 groups of 15 animals that were exposed on day 0 of the experiment to one of the six isolates tested or were mock infected (negative control group). Clinical signs and rectal temperatures were recorded daily and blood samples were taken on days 3, 6, 9, 12, 15, 18 and 21 of the experiment. On days 7, 14 and 21 post-inoculation five animals per group were sacrificed, macroscopic lung lesions were evaluated and different tissue samples were collected to determine viral organic distribution. The results obtained indicate that type 2 isolates are more pneumovirulent than type 1 isolates, as demonstrated by the recording of respiratory clinical signs only in pigs exposed to type 2 viruses and by the severity of macroscopic and microscopic lung lesions in those pigs. However, no clear differences could be established between genotypes in systemic clinical signs or viral load and viral distribution after challenge. These results support the general idea that type 2 isolates induce more severe respiratory disease than type 1 isolates.

Copyright © 2011 Elsevier B.V. All rights reserved.

PMID:

 

21831539

 

[PubMed - as supplied by publisher]

Clin Vaccine Immunol. 2011 Aug 10. [Epub ahead of print]

Effect of the modified live porcine reproductive and respiratory syndrome virus (PRRSV) vaccine on European and North American PRRSV shedding in semen from infected boars.

Han K, Seo HW, Shin JH, Oh Y, Kang I, Park C, Chae C.

Source

Department of Veterinary Pathology, College of Veterinary Medicine, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.

Abstract

The objective of the present study was to compare the effects of the modified live porcine reproductive and respiratory syndrome virus (PRRSV) vaccine (Ingelvac PRRS MLV, Boehringer Ingelheim Animal Health, St. Joseph, MO, USA) on European and North American PRRSV shedding in the semen of experimentally infected boars. The boars were randomly divided into six groups. Vaccinated boars shed the North American PRRSV at the rate of 10(0.1) to 10(1.0) viral genome copies per ml and 3.63 to 10(1.1) 50% tissue culture infective doses (TCID(50))/ml, respectively in semen, whereas non-vaccinated boars shed the North American PRRSV at the rate of 10(0.2) to 10(4.7) viral genome copies per ml and 1.14 to 10(3.07) TCID(50)/ml, respectively in semen. Vaccinated boars shed the European PRRSV at the rate of 10(0.1) to 10(4.57) viral genome copies per ml and 1.66 to 10(3.10) TCID(50)/ml, respectively in semen, whereas non-vaccinated boars shed the European PRRSV at the rate of 10(0.3) to 10(5.14) viral genome copies per ml and 1.69 to 10(3.17) TCID(50)/ml, respectively in semen. The number of genomic copies of the European PRRSV in semen samples was not significantly different between vaccinated and non-vaccinated challenged European PRRSV boars. The present study demonstrated that boar vaccination using commercial modified live PRRSV vaccine was able to decrease subsequent shedding of North American PRRSV in semen after challenge but was unable to decrease shedding of European PRRSV in semen after challenge.