The role of co-infections in M. hyopneumoniae outbreaks among heavy fattening pigs: a field study

Little is known about how co-infections and genotype dynamics affect Mycoplasma hyopneumoniae infection in fattening pigs. This study was aimed at assessing the role of co-infections in M. hyopneumoniae outbreaks, their influence on the presence of M. hyopneumoniae genotypes and their impact on consequent lung lesions. Tracheobronchial swabs (TBS) from 300 finishers were collected from 10 farms at the onset of enzootic pneumonia outbreaks and 1 month later, sampling of 3 groups per farm: Group A showed clinical signs first, Group B was housed near Group A, and Group C was located in a different building. Pigs’ lungs were scored at the slaughterhouse. TBS were tested for the main pathogens involved in respiratory diseases, and samples positive for M. hyopneumoniae were genotyped by multiple-locus variable-number tandem repeat analysis (MLVA). Pigs in Group A showed the highest prevalence and load of M. hyopneumoniae. A positive association was detected between M. hyopneumoniae and Mycoplasma hyorhinis, whereas Actinobacillus pleuropneumoniae was more frequent when the M. hyopneumoniae load was higher. Nevertheless, co-infection had no effect on lung lesion scores. The presence of multiple MLVA types (mixed infections) increased in time only in pigs from Group C and was positively associated with porcine reproductive and respiratory syndrome virus infection. Lung lesions were more severe in pigs with at least one TBS positive for M. hyopneumoniae and in pigs with a history of mixed infections. The central role of M. hyopneumoniae and relevance of mixed infections suggest that increased biosecurity might be beneficial for lung lesion sequelae.

Molecular epidemiology of Leptospira interrogans in Rattus norvegicus in Hanoi, Vietnam

Leptospirosis is a zoonotic disease that is caused by pathogenic spirochaetes of Leptospira spp. and it has become a public health concern in urban localities in the tropics. Rats are important reservoir animals for the transmission of leptospirosis in urban areas. Leptospirosis is considered endemic in Vietnam. However, information on the causative Leptospira genotypes and serotypes in the country is limited. We investigated the carrier status of Leptospira spp. in rats captured in Hanoi by culturing and DNA detection. Isolates were characterized using a serological method and multiple-locus variable-number tandem repeat analysis (MLVA). We captured 144 rats (1 Rattus argentiventer, 135 R. norvegicus, and 8 R. rattus) and obtained 17 L. interrogans, determined by rrs sequencing, from R. norvegicus (12.6%). Sixteen of the isolates were serogroup Bataviae. Five of the 16 isolates exhibited an MLVA type identical to that of the serovar Bataviae reference strain Van Tienen, while there were nine repeats for the other 11 isolates at VNTR31 compared with the reference strain. The remaining isolate grew poorly, and we were unable to determine its serogroup. However, it had an MLVA type matching those of serogroup Pomona strains isolated from R. norvegicus in Japan. Three different flaB sequences were detected in 23 out of 81 R. norvegicus kidney tissue samples (28.4%) using nested PCR followed by DNA sequencing. Two of the sequences were identical with those of serogroups Bataviae and Pomona, and no strain with another sequence was detected in the present study. The present study reveals a high prevalence rate of L. interrogans among R. norvegicus in Hanoi, Vietnam, indicating a potential risk of rat-borne leptospirosis in the area. The present study also demonstrates that a fastidious L. interrogans strain circulates among rats and that molecular detection is crucial in facilitating the accurate determination of reservoir animals.

[Source tracing of the Yersinia pestis strains isolated from Heqing county, Yunnan province in 2017]

Objective: To understand the genotype of the Yersinia (Y.) pestis strains isolated from Heqing county, Yunnan province in 2017 and provide evidence for the prevention and control of plague in this area. Methods: Ten Y. pestis strains isolated from Heqing were typed by the detections of different region (DFR) and clustered regularly interspaced short palindromic repeats (CRISPRs) as well as multiple-locus variable-number tandem repeat analysis (MLVA). And the results were compared with those of the 93 Y. pestis strains from the adjacent plague foci of Heqing obtained from the established database for clustering analysis. Results: The results showed that Heqing strains had the same type of DFR (Genomovar 05) and CRISPRs (Cluster Ca7, Type 22) with isolates from the plague focus in Lijiang. Heqing strains and Lijiang strains were in the same cluster in MST and only VNTR loci N2117 and M23 of Heqing strains were different from that of Lijiang strains. Conclusion: The Y. pestis strains isolated from Heqing in 2017 were highly homogenous with the strains isolated from wild rodents in plague focus in Lijiang, and Heqing plague might be the result of further southward spread of Lijiang plague.

Multiple-locus variable-number tandem repeat analysis of Leptospira interrogans and Leptospira borgpetersenii isolated from small feral and wild mammals in East Asia

Leptospira spp. are the causative agents of a worldwide zoonosis, leptospirosis, maintained by various mammals. Each Leptospira serovar is frequently associated with a particular maintenance host, and recently, Leptospira genotype-host association has also been suggested to limit serovars to restricted areas. We investigated the molecular characteristics of L. interrogans and L. borgpetersenii which were isolated from small feral and wild animals in four East Asian states using multiple-locus variable-number tandem repeat analysis (MLVA). MLVA using 11 loci was performed on 110 L. interrogans serogroups from Japan (79 strains of 5 serogroups from 3 animal species), Philippines (21; 3; 2), Taiwan (7; 2; 3), and Vietnam (3; 1; 1). A MLVA method using 4 loci for L. borgpetersenii was established and performed on 52 isolates from Japan (26; 3; 7), Philippines (13; 1; 2), and Taiwan (13; 1; 3). In L. interrogans, serogroups Autumnalis and Hebdomadis appeared more genetically diverse than serogroups Bataviae, Grippotyphosa, Icterohaemorrhagiae, Pomona, or Pyrogenes. The former serogroup strains with the exception of one Hebdomadis strain were isolated from Apodemus speciosus while all the latter serogroup strains with the exception of Grippotyphosa were isolated from Rattus norvegicus. L. borgpetersenii was isolated from at least 11 animal species while L. interrogans was isolated from five species, which might suggest a wider host range for L. borgpetersenii. Broad host preference in a single genotype was also observed, which colonized not only different species of the same genera but also multiple animal genera. This study demonstrates that there may be variability in the range of genetic diversity among different Leptospira serogroups, which may be attributed to maintenance host animals and environmental factors.