Host Pathogen Interactions: Salmonella in Dairy Cattle

Host Pathogen Interactions

Salmonella Significance

• Higher prevalence is linked to:

  • Large herd size.

  • Use of flush alleys.

• Causes disease and production losses in cattle.

• Presents a public health concern:

  • Zoonotic pathogen (found in beef and dairy products).

  • Emergence of antimicrobial-resistant strains.

• It's zoonotic, similar to cryptosporidium and rotavirus which also cause disease in calves.

Pathogen Characteristics

• Facultative anaerobe.

• Facultative intracellular pathogen.

• Survives in a pH range of 4.5 - 9.

• Multiplies at temperatures of 8 to 45°C.

• Requires a water activity of >0.95 to multiply.

• Survives in dust and feces for years.

Host Specificity

• Can affect humans, all species of livestock, wildlife, reptiles, birds, and insects.

Herd Investigation

• Dry-lot dairy milking 10,000 cows is under investigation.

• The herd is expanding.

• Rolling herd average is 10,000 liters.

• There are 24,000 livestock on the premise.

• Farming operation involves 2,500 irrigation.

Milk Production and Gossypol Content

• Relationship between milk production and feeding cottonseed with high gossypol content is evaluated.

Diagnostic Investigation

• Salmonella cultures are performed on feces and tissues (25/30).

  • Results: S. typhimurium (21), S. give (7), S. kentucky (6), S. hadar (1), S. stanley (1).

• Electron microscopy:

  • Negative for coronavirus (0%).

• Rotavirus ELISA positive (15%).

• Fecal flotation shows Cryptosporidia (22%).

• Gross and histopathology are compatible with salmonellosis.

Calves Clinical Signs

• Incubation Time:

  • Anorexia

  • Fever

  • Diarrhea

  • Death (initially 7-10 days, then 5-7 days).

• Clinical signs are dependent on:

  • Dose.

  • Host immunity.

  • Pathogen virulence.

Adult Cow Investigation

• Fecal cultures show salmonella isolated from 60% of post-parturient cows.

• Necropsies show compatible gross pathology.

• No tissue cultures of adult cows are performed.

Sources of Pathogen Exposure

• Purchased Livestock

• Feed

• Water

• Environment

• Equipment (Rendering trucks)

• People (Veterinarians)

• Wildlife

Salmonella Cultures of Feed Samples

Observations

• Introduced by contaminated feed.

• Feed contaminated by irrigation water.

• Irrigation water contaminated by human effluent.

• Herd exposure preceded outbreak by 7 months.

• Salmonellosis in cows precipitated by:

  • Gossypol toxicosis.

  • Unbalanced transition ration.

  • Hot weather.

• Numerous salmonella serotypes isolated.

• Mortality associated with Salmonella typhimurium.

• Contributing factors:

  • Failure of passive transfer.

  • Colostrum pooling.

  • Calf milk handling practices.

Calf Immunity

• Born immunologically naïve.

• Colostrum provides:

  • Antibodies.

  • Energy.

  • Vitamins.

  • Laxatives.

• Colostrum quality depends on:

  • Antibody content.

  • Microbial contamination.

Colostrum Management

• Key questions to consider:

  • When do you harvest colostrum?

  • What do you harvest it with?

  • Where do you store it?

  • How do you give it?

  • If using an esophageal feeder, is it also used to give fluids to sick calves?

Assessment of Microbial Contamination

• Important to assess microbial contamination in colostrum.

Salmonella Cultures of Individual Cow Milk Samples

Mitigate Risk of Contaminated Milk

• Avoid feeding “Waste” or “Hospital Milk”.

• Pasteurize.

• Refrigerate milk during storage.

• Feed milk replacer.

Variables Influencing Calf Immunity

• Cow Health (Gestation and colostrum production).

• Nutrition (Energy/protein, metabolic).

• Heat Stress (Blood flow to placenta).

• Intra uterine infections (BVD).

• Passive Transfer

  • 150 grams of IgG required.

  • The effectiveness of colostral transfer is determined by cow and calf management.

• Environment

  • Temperature (Heat and Cold increase energy expenditure).

  • Wind.

  • Moisture.

• Nutrition - calves should be fed whole milk at ~ 12 to 15% of their body weight per day.

• Vaccination

Maternal Nutrition (Transition)

• Transition management is linked to reproductive management.

• Accurate conception dates required.

• The right cow on the right ration at the right time and for the correct amount of time.

• 95% of cows calve +/- 14 days and 65 % +/- 7 days of their due date

• Compromised cow leads to compromised calf

Passive Transfer

• Minimum 150 grams IgG per calf

• 50 gm IgG per L of colostrum recommended

• Holstein Brix 22%+, Jersey 18+%

• Colostrum quality influenced by

  • Timing of harvest relative to calving

  • Parity (Cows generally better than heifers)

  • Volume (High volume often lower IgG content than low)

  • Pooling increases risk of transmitting contagious pathogens

• First feed 10 % body weight within 3 hrs

• Second feed 5% around 12 hours of age

• Calves left with cows 65% failure.

• Efficiency of absorption is reduced by ~ 50% by 6-9 hrs of age.

• Assessment of Passive Transfer - Calf Sera 48 hr (Brix > 8.3 %)

Nutrition Birth to Weaning

• Milk / Milk Replacer

• Calf Starter

  • Intake drives rumen development (MEASURE !)

  • Textured promotes intake

  • Dust depresses intake

  • Large volume milk feeding depresses early intake

  • Feed fresh, dispose of spoiled

• Water

  • Ad-lib (restriction depresses dry matter intake)

• Forage

  • Small amount (10 - 15%) mitigates risk of acidosis
    ids \% = 0.9984(Brix\%) + 2.077$$

Milk Replacer

• Pathogen-free as heat-treated during manufacture

• Digestibility influenced by source of ingredients

• Should be milk-based; plant-based proteins are less digestible

• Milk replacer can be fortified (mixed at a higher solids content than milk)

• When feeding fortified milk replacer, care needs to be taken to avoid inducing bloat

• A brix refractometer can be used to check solids content

Milk Storage and Delivery

• Poor storage conditions lead to bacterial proliferation

• Poor hygiene, not refrigerated