Detection of porcine Circovirus type 2 (PCV2) variants PCV2-1 and PCV2-2 in Brazilian pig population

Micoplasma hyopneumoniae associado ao circovírus suíno tipo 2 em plantéis não vacinados para micoplasmose

RESUMO: A síndrome circovirose suína e doenças associadas (PCVAD) tem sido descrita em diversas regiões do mundo. Seu agente primário, o circovírus suíno tipo 2 (PCV2), está associado a elevados índices de refugagem nas granjas e a vultuosos prejuízos econômicos. Diversos fatores de risco estão relacionados à manifestação dos quadros clínicos da síndrome, nomeadamente deficiências de manejo, presença de coinfecções e imunização diante do agente. Entre os agentes frequentemente relatados associados ao PCV2 está o Mycoplasma hyopneumoniae. Este estudo objetivou verificar a ocorrência de M. hyopneumoniae em animais diagnosticados estarem acometidos pela PCVAD, em sistemas intensivos de produção de suínos do estado de Goiás. Amostras de secreção nasal de 40 animais foram analisadas para a pesquisa do DNA de M. hyopneumoniae. Do total das amostras de secreção nasal, 6 (15%) foram positivas na reação em cadeia da polimerase (PCR) para o M. hyopneumoniae, apenas em granjas que não praticavam a vacinação contra esse agente. Os resultados relacionados à presença de micoplasma estão de acordo com os achados clínicos dos animais analisados que apresentavam sintomatologia de doenças respiratórias e lesões relacionadas ao trato respiratório. Este é o primeiro relato da associação de PCV2 com M. hyopneumoniae em suínos identificados com PCVAD no estado de Goiás.

Genetic characterization of porcine circovirus type 2 in captive wild boars in southern Brazil

Porcine circovirus type 2 (PCV2) has been identified in pig population in Brazil since 2000, but scarce studies involving wild boars with PCV2 infection are reported in the country. This study aimed to perform the genetic characterization of PCV2 detected in clinically healthy captive wild boars from farms located in Southern Brazil. Bronchial and mesenteric lymph nodes from 129 clinically healthy captive wild boars were tested by nested PCR for PCV2 detection. Six out of 38 positive samples (29.5%) were submitted to a quantitative real time PCR (qPCR) and genetic sequencing. Viral load up to 1.19 × 10⁹ viral DNA copies/uL was detected in lymph nodes samples by qPCR. According to the ORF2 gene sequence analysis, all PCV2 samples were classified into PCV2b genotype. Comparisons based on a 702 nt region of the ORF2 of all six isolates revealed a high degree of similarity between these isolates. The ORF2 sequences characterized here share 97.1-100% of nucleotide identity and 95.7-100% of amino acid identity with other PCV2b isolated in Brazil from wild boars and feral pigs. This study reports the first detection and genetic characterization of PCV2b in captive wild boars in Brazil and provides important information on PCV2 infection in this domesticated species.

Genetic characterisation of Porcine circovirus type 2 (PCV2) strains from feral pigs in the Brazilian Pantanal: An opportunity to reconstruct the history of PCV2 evolution

Since its discovery, Porcine circovirus type 2 has emerged as one of the most relevant swine infectious diseases, causing relevant economic losses for the pig industry. While four genotypes were identified, only three (PCV2a, PCV2b and PCV2d) are currently circulating and display a worldwide distribution. Another genotype, PCV2c, has been described only once in Danish archive samples collected between 1980 and 1990. In addition to commercial pigs, PCV2 has been demonstrated to infect wild boars and other wild species, which can potentially serve as a reservoir for domestic populations. In this study, eight sequences obtained from feral pigs in the Pantanal region (Mato Grosso do Sul State, Brazil) were compared with reference sequences and other Brazilian sequences, and the results revealed remarkable genetic diversity, with all four genotypes currently recognised being detected (PCV2a, PCV2b, PCV2c and PCV2d). This finding represents a remarkable discovery, as it is the first detection of PCV2c since 1990 and the first-ever detection of PCV2c in live animals. The peculiar population history and ecological scenario of feral pigs in the Pantanal coupled with the complex, and still only partially known relationship of feral pigs with other PCV2 susceptible species (i.e., domestic pigs, wild boars and peccaries), open exciting questions concerning PCV2 origin and evolution. Overall, the results of the present study led us to form the following hypothesis: the PCV2 strains found in feral pigs may be the last descent of the strains that circulated among European pigs in the past, or they may have infected these feral pigs more recently through a bridge species.

Detection and molecular characterization of porcine circovirus type 2 from piglets with porcine circovirus associated diseases in Colombia

BACKGROUND

The porcine circovirus-associated disease (PCVAD) has been known since 1991 in Canada, but the first outbreak of PCVAD in Colombia was reported in 2007. In order to understand the molecular epidemiology of the disease and to establish the origin of the virus in the country, the study presented here intended to evaluate the presence of PCV2-associated systemic infection in piglets from different geographical regions over a period of 9-years (2002-2010). The analysis included samples collected before, during and after outbreaks of PCVAD in pigs from Colombia. The PCV2 ORF2 from the positive samples was sequenced and used to determine the genotypes of the strains and to study the dynamic of these genotypes throughout the time.

RESULTS

PCV2 DNA was detected in cases related to PCV2-associated systemic infection as well as in healthy pigs with a presumable persistent infection. The analysis of the ORF2 nucleotide full length sequence of twenty-three strains allowed to divide them into two groups: PCV2a and PCV2b. At the amino acid level the main variations in the sequence of the capsid protein were found in regions located within the immunoreactive areas.

CONCLUSIONS

The results of this study demonstrated for the first time, that the two subgroups: PCV2a and PCV2b have been circulating in swine from Colombia. In addition, the study showed that genotype PCV2b is present in Colombian pigs suffering from both clinical and presumable persistent infection and that the PCV2b genotype was present in the Colombian pig population even before recognition of the disease in the country and it became predominant through time.

Serological Survey of Porcine circovirus-2 in Captive Wild Boars (Sus scrofa) from Registered Farms of South and South-east Regions of Brazil

This study aimed to survey captive wild boars for antibodies against Porcine circovirus-2 (PCV-2) in registered farms. Serum samples (n = 1305) were collected from 90-day-old wild boars from 118 farms of the Brazilian South-east region, including the states of Minas Gerais and São Paulo, and South region, including the states of Paraná, Rio Grande do Sul and Santa Catarina. All herds (100%) presented reactive animals, in varying numbers and from low-to-high antibody titres, with the occurrence ranging from 82 to 89%. Considering farms, the average prevalence was of 84.9% (P < 0.05) and ranged from 54.1 to 94.95%. Regarding the geographic regions studied, the prevalence was of 100%, with PCV2 antibodies detected in wild boars of all regions. This study provides the first evidence of PCV2 antibodies in captive wild boars in Brazil.

Efficacy and future prospects of commercially available and experimental vaccines against porcine circovirus type 2 (PCV2)

Porcine circovirus type 2 (PCV2) is the causative agent of an economically significant collection of disease syndromes in pigs, now known as porcine circovirus associated diseases (PCVADs) in the United States or porcine circovirus diseases (PCVDs) in Europe. Inactivated and subunit vaccines based on PCV2a genotype are commercially available and have been shown to be effective at decreasing mortality and increasing growth parameters in commercial swine herds. Since 2003, there has been a drastic global shift in the predominant prevalence of PCV2b genotype in swine populations, concurrently in most but not all cases with increased severity of clinical disease. Although the current commercial vaccines based on PCV2a do confer cross-protection against PCV2b, novel experimental vaccines based on PCV2b genotype such as modified live-attenuated vaccines are being developed and may provide a superior protection and reduce vaccine costs. In this review, we discuss the current understanding of the impact of PCV2 infection on the host immune response, review the efficacy of the currently available commercial PCV2 vaccines in experimental and field conditions, and provide insight into novel experimental approaches that are useful in the development of next generation vaccines against PCV2.

Genetic characterization of porcine circovirus type 2 from pigs with porcine circovirus associated diseases in Argentina

Porcine circovirus type 2 (PCV-2) has been associated with syndromes grouped by the term porcine circovirus associated diseases (PCVAD). The PCV-2 isolates have been grouped into two major groups or genotypes according to their nucleotide sequence of whole genomes and/or ORF-2: PCV-2b, which have, in turn, been subdivided into three clusters (1A-1C), and PCV-2a, which has been subdivided into five clusters (2A-2E). In the present study, we obtained 16 sequences of PCV-2 from different farms from 2003 to 2008, from animals with confirmatory diagnosis of PCVAD. Since results showed an identity of 99.8% among them, they were grouped within a common cluster 1A-B. This preliminary study suggests a stable circulation of PCV-2b among the Argentinean pig population.

Genetic characterization of porcine circovirus type 2 in piglets from PMWS-affected and -negative farms in Thailand

Porcine circovirus type 2 (PCV2) is the major swine pathogen associated with Porcine circovirus associated disease (PCVAD) including post-weaning multisystemic wasting syndrome (PMWS). Currently, there are 4 subtypes of PCV2 (PCV2a, b, c and d) and some epidemiological evidences demonstrated that virulence of PCV2 may relate to its subtypes. Recently, PMWS was observed more frequently in swine farms in Thailand; however, the information regarding to PCV2 subtype involved was limited. Therefore, this study was aimed to determine the association between occurrence of PMWS and PCV2 subtypes as well as genetically characterize PCV2 in Thailand. PCV2 DNA was isolated from faecal swabs and whole blood of piglets from PMWS-affected and -negative farms. The full length ORF2 sequences were compared using multiple alignment. The results showed that PCV2 DNA was detected more frequently in PMWS-affected farms. The nucleotide identities of the ORF2 from 9 PCV2 isolates representing each PMWS-affected farm and one from the negative farm ranged from 92.4 to 99.5% suggesting that there is some genetic variation of PCV2 in Thai swine. The 10 PCV2 isolates were classified into 2 clusters, in which the 7 isolates from PMWS-positive farms were in PCV2b cluster 1 A/B. The remaining isolates were separated in the new subtype called PCV2e. The results suggest the presence of new PCV2 subtypes in addition to PCV2a and PCV2b in Asian swine population. However, correlation between subtypes and virulence of PCV2 infection is not conclusive due to limited number of the PCV2 sequences from PMWS negative farms.

Multiply-primed rolling-circle amplification (MPRCA) of PCV2 genomes: applications on detection, sequencing and virus isolation

Multiply-primed rolling-circle amplification (MPRCA) was used to amplify porcine circovirus type 2 (PCV2) genomes isolated from tissues of pigs with signs of post-weaning multisystemic wasting syndrome (PMWS). Two of the amplified PCV2 genomes were cloned in prokaryotic plasmids and sequenced. Both were nearly identical (1767 nt) except for one silent substitution in the region coding for the capsid protein (ORF2). In addition, they showed high nucleotide sequence similarity with PCV2 isolates from others countries (93-99%). To investigate whether the MPRCA amplified PCV2 genomes could be used to produce infectious virus, the cloned genomes were isolated from the plasmids, recircularized and used for transfection in PK-15 cells. This procedure led to the production of infectious virus to titres up to 10(5.55) TCID(50)/mL. It was concluded that MPRCA is a useful tool to amplify PCV2 genomes aiming at sequencing and virus isolation strategies, where particularly useful is the fact that it allows straightforward construction of PCV2 infectious clones from amplified genomes. However, it was less sensitive than PCR for diagnostic purposes.