Elsevier

Veterinary Microbiology

Volume 181, Issues 3–4, 31 December 2015, Pages 308-312
Veterinary Microbiology

Short communication
The upper respiratory tract is a natural reservoir of haemolytic Mannheimia species associated with ovine mastitis

https://doi.org/10.1016/j.vetmic.2015.10.006Get rights and content

Highlights

  • Mannheinmia haemolytica and Mannheimia glucosida as well as haemolytic Mannheimia ruminalis-like organisms were detected in the upper respiratory tract of lambs and ewes.

  • There was some evidence indicating the Mannheimia species strains that inhabit the nasopharynx of sheep also have the capacity to cause mastitis.

  • More diversity was seen in the M. haemolytica isolates inhabiting the nasopharynx of sheep than that in the M. glucosida isolates.

Abstract

Lamb suckling has been suggested to be an important way of infecting a ewe's udder with different bacteria, including Mannheimia haemolytica. To test the potential role of lambs in transferring Mannheimia species to the ewe’s udder, the restriction endonuclease cleavage patterns of isolates obtained from nasopharyngeal swabs were compared with those obtained from cases of mastitis. Sterile cotton swabs were used to collect nasopharyngeal samples from 50 ewes and 36 lambs from three flocks. M. haemolytica and Mannheimia glucosida as well as haemolytic Mannheimia ruminalis-like organisms were detected in the upper respiratory tract of lambs and ewes. Comparison of the restriction endonuclease cleavage patterns of the isolates suggested that the M. haemolytica isolates obtained from different milk samples from ewes with mastitis were more clonal than those obtained from the nasal swabs. However, some nasal isolates within both Mannheimia species had restriction endonuclease cleavage patterns identical to those obtained from milk samples from ewes with mastitis, indicating that lambs may have a role in transferring these organisms to the udder. More clonality was observed between the M. glucosida isolates than between M. haemolytica isolates.

Introduction

Mannheimia haemolytica is an opportunistically pathogenic organism and an obligate commensal of the upper respiratory tract of ruminants. It is the major organism involved in bovine respiratory disease and can cause ovine pneumonia and septicaemia (Boyce et al., 2004, Kirk and Glenn, 1996). Together with Mannheimia glucosida, they are known to be important causes of intramammary infection in sheep (Omaleki et al., 2010, Omaleki et al., 2011). Lamb suckling has been suggested as an important route for transferring M. haemolytica from the nasopharynx of lambs to the ewe’s udder, as isolates obtained from the ovine respiratory tract had similar pathogenicity for ovine mammary tissue to those obtained from mammary secretions or mastitic milk (Fragkou et al., 2011). Studies have demonstrated that M. haemolytica cannot be isolated from the teat skin before lambing or after weaning, also indicating the likely role of lambs in transferring this organism from their oral cavity to the ewe’s udder (Jones and Watkins, 1998). Colonisation of papilloma-like scabby lesions of the teat with different serotypes of M. haemolytica, including serotype A11 of the former [P.] haemolytica, latterly reclassified as M. glucosida, has also been reported, suggesting that these lesions can act as a source for contamination of the teat canal after lamb suckling (Burriel, 1997).

There are no published data investigating the genetic associations between isolates of Mannheimia species from the nasopharynx of sheep and those causing mastitis. Therefore, this study aimed to identify isolates of M. haemolytica and M. glucosida from the nasopharynx of sheep and compare the isolates previously found to be associated with ovine mastitis with those obtained from nasal swabs.

Section snippets

Materials and methods

Three Poll Dorset flocks were included in this study. Flock A had a history of clinical mastitis caused by Mannheimia species at a prevalence of up to 5% over the previous three years, flock J had had a mastitis outbreak in 2009 with 10% of lactating ewes affected (Omaleki et al., under revision), and flock K had had a prevalence of mastitis of less than 2% over the past three years. The three flocks were located in different regions of Victoria, Australia: flock A in the north-east, flock J in

Results

Haemolytic Mannheimia sp. isolates were obtained from 13 of the 26 nasal swabs collected in flock A (50%), with 4 of them identified as M. haemolytica and 9 as M. glucosida (31% and 69% of the haemolytic Mannheimia spp. isolates respectively) (Supplementary Table 1). The nasal swab isolates from this flock were designated with a lower case letter “a”. In this flock, the M. haemolytica isolate a11, obtained from a nasal swab of a lamb in December 2010, was closely related to mastitis isolates

Discussion

Lamb suckling has been suggested to be an important means of infecting the ewe’s udder with different bacteria, as an increase in bacteriologically positive teat secretions of ewes is observed after they have suckled their lambs (Fragkou et al., 2011, Gougoulis et al., 2008). In one study, M. haemolytica was isolated from 63% of samples collected from the tonsils of lambs over 6 weeks (Fragkou et al., 2011). Comparison of the 16s rRNA gene sequence of a M. haemolytica isolate obtained from milk

Conflict of interest

The authors declared that they had no conflicts of interest with respect to their authorship or the publication of this article.

References (19)

There are more references available in the full text version of this article.

Cited by (5)

  • Dynamics of intramammary infections in suckler ewes during early lactation

    2021, Journal of Dairy Science
    Citation Excerpt :

    Possibly, the transmission of this pathogen is limited early in lactation and increases only later in lactation. It has been shown that lambs are the likely vectors of M. haemolytica because they carry the pathogen in their nasopharynx and are capable of infecting the udder during suckling (Gougoulis et al., 2008; Omaleki et al., 2015). If lambs are responsible for the transmission of mastitis pathogens, it is difficult to understand why we saw a strong increase in the prevalence of Staph.

View full text