Vaccination of neonatal pigs with MLV PRRSV vaccine is able to overcome maternal immunity

Porcine Health Manag. 2018 Nov 15;4:25. doi: 10.1186/s40813-018-0101-x. eCollection 2018.

Vaccination of 1-day-old pigs with a porcine reproductive and respiratory syndrome virus (PRRSV) modified live attenuated virus vaccine is able to overcome maternal immunity.

Balasch M1, Fort M1, Taylor LP2, Calvert JG2.

Author information

Abstract

BACKGROUND: 

The objective of the study was to evaluate the influence of maternally derived antibodies (MDA) on the efficacy of a PRRSV-1 based attenuated vaccine, when administered in 1 day-old piglets by the intramuscular route. The protective immunity of the modified live virus vaccine was evaluated in pigs born from seropositive sows, vaccinated at 1 day of age, upon inoculation with a PRRSV-1 isolate. The animals were challenged when the levels of MDAs detected by seroneutralization test (SNT) in the non-vaccinated control group became undetectable (10 weeks after vaccination).

RESULTS: 

A protective effect of vaccination was observed since a significant reduction of viral load in serum compared to the control group was detected in all sampling days after challenge; efficacy was supported by the significant reduction of nasal and oral shedding as well as in rectal temperatures. Clinical signs were not expected after the inoculation of a PRRSV-1 subtype 1 challenge strain. However, the challenge virus was able to develop fever in 61% of the control pigs. Vaccination had a positive impact on rectal temperatures since the percentage of pigs that had fever at least once after challenge was reduced to 31% in vaccinated animals, and control pigs had significantly higher rectal temperatures than vaccinated pigs 3 days post-challenge. The lack of a vaccination effect in body weight gain was probably due to the short evaluation period after challenge (10 days). In the vaccinated group, 9/16 pigs (56%) experienced an increase in ELISA S/P ratio from the day of vaccination to 67 days post-vaccination. All vaccinated pigs were seropositive before challenge, indicating the development of an antibody response following vaccination even in the face of MDAs. In contrast to ELISA results, only 2/16 vaccinated pigs developed neutralizing antibodies detectable by a SNT that used a subtype 1 MA-104 adapted strain. Even in the absence of SN antibodies, vaccinated pigs were protected from challenge with a heterologous strain. The role of cell-mediated immunity should be considered, if protection was not mediated by SN antibodies only.

CONCLUSIONS: 

The efficacy of the attenuated PRRSV-1 vaccine in 1-day-old pigs seropositive to PRRSV prior to a PRRSV-1 challenge was demonstrated by improvement of clinical, virological and immunological variables. With the current experimental design, maternal immunity did not interfere with the development of a protective immune response against a PRRSV-1 challenge, after vaccination of 1 day-old pigs. Confirmation of these results under field conditions will be needed.

KEYWORDS: 

Maternal-derived immunity; Modified live vaccine; Porcine reproductive and respiratory syndrome

PMID:

 

30459958

 

PMCID:

 

PMC6237022

 

DOI:

 

10.1186/s40813-018-0101-x

Biosecurity scoring system for PRRS - measure and benchmark vulnerability to PRRS infection!

Prev Vet Med. 2018 Nov 15;160:116-122. doi: 10.1016/j.prevetmed.2018.10.004. Epub 2018 Oct 10.

Development and validation of a scoring system to assess the relative vulnerability of swine breeding herds to the introduction of PRRS virus.

Silva GS1, Corbellini LG2, Linhares DLC3, Baker KL3, Holtkamp DJ4.

Author information

1

Veterinary Diagnostic and Production Animal Medicine Department, Iowa State University, Ames, IA, United States; Laboratory of Veterinary Epidemiology (Epilab), Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.

2

Laboratory of Veterinary Epidemiology (Epilab), Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.

3

Veterinary Diagnostic and Production Animal Medicine Department, Iowa State University, Ames, IA, United States.

4

Veterinary Diagnostic and Production Animal Medicine Department, Iowa State University, Ames, IA, United States. Electronic address: holtkamp@iastate.edu.

Abstract

Biosecurity is defined as the set of practices carried out to prevent the introduction and spread of infectious agents in a herd. These practices are essential in swine production, especially for highly infectious agents such as porcine reproductive and respiratory syndrome virus (PRRSv). Even with years of research and experience over the last three decades, PRRSv is still causing productivity losses and is the major health problem affecting the global swine industry. Despite knowledge of the various ways in which the virus can be transmitted from one herd to another (e.g. animals, semen, truck, air, and people), determining the most frequent ways in which the virus is transmitted in the field is difficult. A systematic approach to assess vulnerabilities at a herd level related to PRRSv transmission could help producers prioritize biosecurity practices to reduce or avoid the occurrence of outbreaks. The aim of this study was to develop a biosecurity vulnerability score that represents the relative vulnerability of swine breeding herds to the introduction of PRRSv. To create the biosecurity vulnerability score (outcome), a multi-criteria decision analysis methodology was used to rank and quantify biosecurity practices based on expert opinion. To validate the biosecurity vulnerability score, a survey of biosecurity practices and PRRS outbreak histories in 125 breed-to-wean herds in the U.S. swine industry was used. Data on the frequency of PRRS outbreaks was used to test the hypothesis that biosecurity vulnerability scores were different between farms that have a low incidence of PRRS outbreaks, compared to farms that have a high incidence. In the two databases used, the scores consistently showed that farms with higher scores have a higher frequency of PRRS outbreaks. In the first validation, farms that had never had an outbreak investigation before had a significant (p < 0.02) lower score (0.29; 0.21-0.37) when compared to farms that had 2 or more outbreaks (0.43; 0.39-0.46). In the second, the farms of the control group also had significant (p < 0.004) lower scores (0.30; 0.27-0.33) compared to the case group (0.35; 0.33-0.38). Also, the results suggest that events related to swine movements, transmission by air and water, and people movements should be prioritized. The biosecurity vulnerability scores may be useful to assess vulnerabilities on biosecurity protocols in order to reduce the frequency of PRRS outbreaks and may help producers and veterinarians prioritize investments in improving biosecurity practices over time.

KEYWORDS: 

Biosecurity; Biosecurity vulnerability score; Carrying agents; PRRS; Risk events; Swine farms

PMID:

 

30388993

 

DOI:

 

10.1016/j.prevetmed.2018.10.004