Sources of Intramammary Infections from Staphylococcus aureus in Dairy Heifers at First Parturition

Abstract

The study objective was to identify probable sources and modes of transmission of 91 Staphylococcus aureus isolates obtained from the colostrum of 76 heifers at parturition. Sources cultured were milk (including colostrum), heifer body sites (teats, muzzle, rectum, vagina, and lacteal secretions), and environmental sites (bedding, insects, housing, water, feedstuffs, humans, nonbovine animals, air, and equipment). Staphylococcus aureus isolates were characterized by 63 phenotypic traits. A similarity coefficient was calculated by herd to identify the S. aureus that most closely resembled the S. aureus obtained from heifer colostrum. Staphylococcus aureus from a heifer's colostrum was compared with all preexisting S. aureus isolates from that heifer's herd. Isolates that were > or = 90% similar were considered to be identical. Because 30 (of the 91) S. aureus isolates from heifer colostrum were collected prior to environmental sampling, only 61 S. aureus isolates from heifer colostrum were available for comparison among all three sources. Possible sources of S. aureus from heifer colostrum at parturition were milk (70%, 43 of 61 isolates), heifer body sites (39%, 24 of 61), environmental sites (28%, 17 of 61), or no identified source (16%, 10 of 61). Three heifers with intramammary infection (IMI) from S. aureus at parturition had the same S. aureus on their teats prior to parturition. Milk was the only source identified for 41% (25 of 61) of isolates from heifer colostrum. Isolates from heifer body sites were the only source identified for 5% (3 of 61) of heifer colostrum isolates. Staphylococcus aureus from the environment was never the sole possible source for S. aureus from heifer colostrum. Data suggest that the major sources of S. aureus IMI in heifers at parturition are milk and heifer body sites. Contact among heifers may be an important mode of transmission of S. aureus leading to IMI in heifers at parturition.

Epidemiological Analysis of Staphylococcus aureus Isolated from Cows and the Environment of a Dairy Farm in Japan

“…Feeding of unpasteurized milk and close contact with carriers may be one reason for the spread of S. aureus to heifers, with this farming practice possibly leading to heifer mastitis. Furthermore, heifers purchased as replacements seem to be an important causal factor of IMI due to S. aureus [19,23]. According to the MLST website and previous reports, S. aureus strains from pets have similar genotypes to those aureus isolated from different samples in the dairy farm monitored.…”

“…It has long been suspected that S. aureus is an important causal bacterium of bovine mastitis [4]. Although the lactating mammary gland is regarded as the primary reservoir of S. aureus in intramammary infection (IMI) [5,21], the bacterium has also been isolated from the dairy farm environment [17,23]. Epidemiological studies are necessary to establish effective preventive measures.…”

Alternativas en el manejo de la mastitis en novillas

“…El mayor problema asociado con la mastitis en novillas al momento del parto es el incremento en el recuento de CS (31). Durante las semanas de IIM subclínica las novillas afectadas contribuyen a elevar el recuento de CS del hato en general, reduciendo notoriamente la calidad de la leche.…”

“…Algunos de los SCN son parte de la flora normal de la piel de los bovinos e incluyen las especies Staphylococcus simulans, Staphylococcus hyicus y Staphylococcus epidermis; otros se encuentran en el ambiente como las especies resistentes a la novobiocina. Los SCN son oportunistas e infectan el canal del pezón y la glándula mamaria desde la piel, por esto se ubican entre los patógenos asociados con la mastitis bovina en el grupo de organismos ambientales (31,40 …”

Genetic management of infectious diseases: a heterogeneous epidemio-genetic model illustrated with S. aureus mastitis

“…While modeling the spread of S. aureus mastitis, udder quarters instead of heifers were treated as individual units because exposed quarters are the units at risk of infection by S. aureus [25]. Infectivity was assumed constant for all infected cow-quarters even if doses of infectious material may vary between quarters and during the course of the disease [37].…”