Mastitis

From Cow
Clinical appearance of acute mastitis in the cow
Per-acute gangrenous mastitis in a cow
Acute Streptococcus agalactiae mastitis in a cow

Bovine mastitis is an inflammatory mammary gland disease usually caused by bacterial infection. Mastitis occurs in cattle worldwide and of significant economic importance. Mastitis may occur in peracute, acute and chronic forms.

Cause

Mastitis is caused by genetic predisposition, trauma, and secondary infection with a wide range of pathogens; bacteria, mycoplasma and funguses. Lower levels of antibacterial components in bovine mammary secretion during the peripartum period may reduce the natural defense potential of the gland[1].

Bacteria incriminated in bovine mastitis include:

S. dysgalactia, S. uberis
S. aureus, coagulase-negative staphylococci (CNS)

Fungi incriminated in bovine mastitis include:


The majority of cases are caused by direct infection by Streptococcus spp, Staphylococcus spp and lactose-fermenting coliforms such as Escherichia coli. Streptococcus agalactiae is a contagious mastitis bacterium, often associated with cases of subclinical mastitis[2]. Serratia liquefaciens mastitis has been reported in cows secondary to frost-bite[3].

Except for Mycoplasma spp, which may spread from cow to cow through aerosol transmission and invade the udder subsequent to bacteremia, contagious pathogens are spread during milking by milkers' hands or the liners of the milking unit. Species that utilize this mode of transmission include Staphylococcus aureus, Streptococcus agalactiae, and Corynebacterium bovis. Most other species are opportunistic invaders from the cow's environment, although some other streptococci and staphylococci may also have a contagious component.

The bedding used for housing cattle is the primary source of environmental pathogens, but contaminated teat dips, intramammary infusions, water hoses used for udder preparation during milking, water ponds or mud holes, skin lesions, teat burns, teat frost-bite, and flies have all been incriminated as sources of infection[4].

Clinical signs

Low-grade or subclinical mastitis results in changes to the milk, resulting in milk loss to human consumption. Acute mastitis results in pain, fever, anorexia and in severe cases, shock.

Staphylococcus aureus intramammary infections often result in deep-seated abscesses and toxic shock[5].

Diagnosis

Diagnosis is determined based on presenting clinical signs and examination of milk for somatic cell counts (predominantly neutrophils)[6]. Cows with a somatic cell count of ≥280,000 cells/mL have a >80% chance of being infected. Likewise, the higher the somatic cell count in a herd bulk tank, the higher the prevalence of infection in the herd.

Causative agents must be identified by bacterial culture of milk.

Treatment

Most gram-negative udder pathogens are multidrug resistant and require multi-drug therapy[7].

Numerous commercial products are available; the majority contain penicillin, cloxacillin, cephapirin, or a macrolide such as erythromycin or novobiocin. One tube per quarter is sufficient and should be administered immediately after the last milking of lactation. Therapy should not be repeated by intramammary infusion; if there is a need to extend therapy, systemic administration should be used as an adjunct to the intramammary infusion. In addition to eliminating existing subclinical infections, one of the most critical roles of dry cow therapy is the prevention of new infections. However, most commercial dry cow products have little or no activity against gram-negative pathogens, and their administration at the start of the dry period will not be effective against new infections that begin during the periparturient period.

Prevention relies upon regular monitoring of somatic cell counts to isolate and treat potential recurrent clinical cases[8].

References

  1. Sordillo LM et al (1987) Secretion composition during bovine mammary involution and the relationship with mastitis. Int J Biochem 19(12):1165-1172
  2. Akerstedt M et al (2012) Protein degradation in bovine milk caused by Streptococcus agalactiae. J Dairy Res 79(3):297-303
  3. Bowman GL et al (1986) Serratia liquefaciens mastitis in a dairy herd. J Am Vet Med Assoc 189(8):913-915
  4. Morton JM et al (1987) Teat burns in dairy cattle - the prognosis and effect of treatment. Aust Vet J 64(3):69-72
  5. Jones TO & Wieneke AA (1986) Staphylococcal toxic shock syndrome. Vet Rec 119(17):435-436
  6. Merck Vet Manual
  7. Saini V et al (2012) Antimicrobial resistance profiles of common mastitis pathogens on Canadian dairy farms. J Dairy Sci 95(8):4319-4332
  8. Blowey RW (1986) An assessment of the economic benefits of a mastitis control scheme. Vet Rec 119(22):551-553