Virus Kills Cells of Intestinal Villi, Leading to Malabsorbtion Diarrhea

Rotavirus

Other causes of calf diarrhea including E. coli, Salmonella spp., Clostridium, Campylobacter, Rotavirus, Coronavirus, BVD, Cryptosporidium, Eimeria, and Giardia. Simple explanations!

Corona Diarrhea

-Virus kills cells of intestinal villi, leading to malabsorbtion diarrhea.

-Infected calves begin shedding 1011 virus per gram of feces about 3 days after infection.

-Carrier cows in the herd shed low numbers of virus.

-Virus survives in the environment for weeks.

-Vaccines are available although not always efficacious.

-Antibiotics are ineffective (virus).

FAMILY

The rotavirus is from the viral family Reoviridae. Rotavirus is a non-enveloped double stranded RNA virus. The name is derived from the wheel-like spokes radiating from the centre because “rota” in latin means wheel.

DIAGRAM / PICTURE

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CHARACTERISTICS

Everything about morphology, classifications, and strains

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• 70-85nm diameter, nearly spherical icosahedral particles
• Non-enveloped, capsid = double shell of proteins
• Genome = 10-12 segments d/s RNA
• Replication: occurs in cytoplasm; incomplete uncoating of virions, which possess all the enzymes required for d/s RNA transcription (not in cells!)

This family is ubiquitous in nature - infecting invertebrates, vertebrates and plants. Abs have been found in all species of mammals tested (except whales), implying wide cell tropism/ubiquitous receptor

CLINICAL SIGNS (

Rotaviral infections are often seen in suckling calves 5-15 days old. Major signs of rotaviral infection in calves are profuse mucoid diarrhea, dehydration, and profound weakness that proceeds to death.

The Merck Veterinary Manual. 2005. Ninth Edition.

• Diarrhea, sometimes containing blood or mucus
• Dehydration, loose skin
• Rough haircoat
• Weight loss, weakness
• Death can occur 12–48 hours after onset of disease

Causes of scours, age of disease onset and clinical signs

Scours agent / Age of onset / Signs
Rotavirus / possible: 0–28 days;
most common: 1–6 days / watery-brown to light-green feces, blood and mucus
K 99 E. coli bacteria / most common: 1–7 days / effortless passing of yellow-to-white feces
Coronavirus / possible: 0–28 days;
most common: 7–10 days / watery, yellow feces
Clostridium perfringens Type C / most common: 7–28 days / sudden death; fetid, blood-tinged diarrhea
Cryptosporidia / most common: 7–21 days / watery-brown to light-green feces, blood and mucus
Coccidia / most common: 7 days and after / blood-tinged diarrhea
Salmonella spp. / most common: 1–7 days / similar to E. coli; yellow-to-white feces

PATHOGENESIS

After ingestion, the rotavirus particles are carried to the small intestine where they infect the mature enterocytes in the mid and upper part of the villi of the small intestine, leading to diarrhea. Rotavirus is thought to invade target cells in two possible ways, by direct entry or fusion with the enterocytes, and through Ca2+-dependent endocytosis.

Rotavirus infection leads to structural changes in the intestinal epithelium. Within 24 hours of infection, the shape of the villus epithelium changes from columnar to cuboidal, and the villi become stunted and shortened. Changes are most severe in the upper portions of the small intestine, and there is little or no inflammation. The severity of these changes is correlated with the severity of the resulting illness.

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TRANSMISSION

Rotavirus spreads between people by fecal-oral transmission

RISK FACTORS

Fecal samples from calves on 78 randomly selected Holstein dairy farms in southwestern Ontario were screened for Salmonella, Campylobacter jejuni/coli, enteropathogenic Escherichia coli, rotavirus and coronavirus. Based on the observed prevalence, 22% of farms had calves infected with Salmonella, 13% with Campylobacter jejuni/coli, 41% with enteropathogenic E. coli, 19% with rotavirus and 5% with coronavirus.

It was found that an increased percentage of heifers calving in the herd, poor drainage in the nursing area, providing limited shelter in the nursing area, a large calving area, and wintering cows and heifers on the same ground were conditionally associated with an increase in the odds of high mortality from neonatal diarrhea.

Risk factors for mortality from diarrhea in beef calves in Alberta.

F J Schumann, H G Townsend, and J M Naylor

Department of Herd Medicine and Theriogenology, WesternCollege of Veterinary Medicine, University of Saskatchewan, Saskatoon.

• Inadequate or insufficient colostrum
• Inadequate quantity colostrum
• Difficult calving
• Poor sanitation
• Cold, wet weather
• Use of milk replacers can result in scours in some cases
• Over-consumption of milk creates an environment in which certain types of bacteria thrive, causing severe scours

IMMUNITY

A natural immune state to rotavirus does not exist. Though primary infection by the virus induces production of rotavirus-specific memory B and T cells, these are not normally sufficient to prevent reinfection by the virus. However, they do serve to reduce the severity of secondary infections.

One reason these antibody responses do not confer full proection is that they are serotype specific. Given the diversity of the various rotavirus serotypes, this prevents these antibodies from mediating full protection against infection by a different serotype. This is also why repeat infections are less severe, as each additional infection expands the population of B cells producing cross-reactive antibodies that can recognize multiple serotypes. Any vaccine effort would need to generate these cross-reactive antibodies to generate effective protection

PROTECTION (VACCINE PROTOCOL)

From the clinical point of view, outbreaks of diarrhoea in calves born of vaccinated cows were less common and less serious, but more importantly, the rotavirus was found to be playing a far less significant role. It was thus demonstrated that the presence of a great quantity of specific antibodies in the intestine plays a protective role.

Passive protection of newborn calves against rotavirus by vaccination of their dams.

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Beef and Dairy Cattle Vaccination Protocols

Novartis Animal Health - Ecostar

Pfizer Animal Health

TREATMENT

It should be directed toward correcting the dehydration, acidosis, and electrolyte loss. Antibiotic treatment can be given simultaneously with the treatment for dehydration. Dehydration can be overcome with simple fluids given by mouth early in the course of the disease. If dehydration is allowed to continue, intravenous fluid treatment becomes necessary. The clinical signs of dehydration first occur when the fluid loss reaches 5 to 6 percent of the body weight. Ten percent loss of fluid results in depression, sunken eyes, dry skin, and the calf will probably be unable to stand. A 15 percent loss of fluids usually results in death. Oral fluids used early in the scouring process have been quite successful. Consult your veterinarian for electrolytes to be given orally. There are dry electrolyte powders available that can be mixed with water for oral administration.

If electrolyte powders are not available, there are three solutions for oral administration that can be prepared on the ranch:

1. Combine 1 can beef consomme, 1 package fruit pectin
   (Sure Jell or Pen Jel),2 teaspoons low sodium salt (Morton Lite Salt), 2 teaspoons baking soda, and add enough warm water to total 2 quarts.
2. Combine 1 can beef consomme, 3 cans warm water, and 1 heaping tablespoon baking soda.
3. Combine 1 tablespoon baking soda, 1 teaspoon salt, and 250 cc (8 ounces) 50% dextrose or 8 ounces light Karo syrup, and add enough warm water to total 1 gallon.

ECONOMICS OF SCOURS

Economically, managing and treating scours is effective to reduce the overall incidence of decreased weaning weights of calves.

Calf scours or calf diarrhea causes more financial loss to cow-calf producers than any other disease- related problem they encounter.

PREVENTION / MANAGEMENT

Maximize the calf’s natural resistance and acquired immunity (colostrum) prior to exposure.

Minimize dystocia, maintain proper nutrition and body condition of dam in critical third trimester of pregnancy.

Delay and minimize the infectious dose that the calf is exposed to.

As most of these agents are ubiquitous (in most herds), calf must eventually acquire the infection and develop an active immunity.

Minimize exposure dose by minimizing density of susceptible calves.

Minimize environmental survival of infectious agents by maximizing drying and exposure to sunlight of potential infectious material (feces)

Move cows and heifers to separate calving area several weeks before calving.

Skin and hair of cows on winter feed and bed ground will have infectious agents shed by carrier cows.
Heifers have poorer colostrum.
Heifers need more supervision.

One day after calving, move pair to large pasture area to spread out.

Exposed calf takes about 3 days to begin shedding agent in large numbers.

If scours develops in a group, leave all of that group in place but turn out new pairs to a new pasture.

More infected calves are subclinical shedders than are clinical cases (The Iceberg Principle).

DO NOT bring in purchased calves to replace dead calves.

They are often colostrum deprived and usually have been exposed to the full gamut of infectious agents.

Cleaning and Disinfection:

Thorough rinsing and cleaning is the first step, whether hutch, hands, or nipples.

Remove all organic matter (feces, blood, milk, milk stone, milk fat, saliva).

Organic matter protects infectious agents from the action of disinfectants (chemical or direct sunlight).

Soap, water, and scrubbing are the most important; mechanically removing the agents.

Decreasing Pathogen Exposure to the Calf:

1. Calving in clean and dry areas.

2. Calve heifers earlier than the cow herd.

3. Avoid congregating

a. Avoid hay feeding in calving pastures by setting aside pastures during the summer to stockpile forage for utilization during calving time.
b. Move pairs to larger pastures promptly
c. If hay is fed, use hay feeders and move feeders frequently.

4. Use biosecurity and biocontainment measures for all herd additions: a. Isolate, quarantine, and perform appropriate tests on all herd additions. (See section on Biosecurity in the Beef Herd)
b. Introduce pregnant herd additions at least 30 days prior to the start of calving season. This will allow time for exposure to new pathogens, antibody development and secretion of antibodies into the colostrum.
c. Do not add calves to the herd until the youngest calf in the herd is over 30 days of age. Buying a calf at a livestock auction or from a dairy for a cow that has lost a calf can introduce diseases that your herd may not have immunity against.

5. Isolation and treatment:

a. Remove sick calves from the herd immediately. One sick calf can produce overwhelming pathogen exposure by shedding as many as 100 million bacteria or viruses per milliliter of feces (500 million bacteria and or viruses per teaspoon of feces).
b. Treating the sick calves should occur after handling the well calves. Clean and disinfect all equipment. Clothing, boots, gloves, etc. worn while treating sick calves should not be worn when handling well calves.

Sampling Protocols For Bovine Neonatal Diarrhea

1. Samples submitted in latex gloves or OB sleeves, or other inappropriate packaging, will not be processed or tested.

2. All test require that strict sample hygiene is used to prevent any cross-contamination between cases.

3. Collect necessary samples. Use a Ziplock bag or Whirlpak bag (no OB sleeves) for each fresh tissues that is collected. DO NOT POOL TISSUES. Clearly label the bag with the name of the owner and the specimen contained with the bag.

4. Collect samples for histopathology. Minimal sampling should include rumen, abomasum, duodenum, jejunum, ileum, colon and any gross lesions of the gastrointestinal tract. Samples should be opened along the mesenteric border to expose the lumen and placed in 10% formalin. Samples of liver, kidney, lung, spleen, and cardiac muscle should also be included in 10% formalin.

5. Collect samples for virology. Ileal contents/scrapings for direct EM exam is preferred (placed in a plastic vial). If BVDV is suspected then additional fresh samples such as distal ileum, mesenteric lymph node, and thymus may be submitted for PCR and/or VI (at additional cost).

6. Collect samples for bacteriology. Samples should include a fresh segment of colon, mesenteric lymph node, and any grossly abnormal tissue. Fresh samples of liver, lung, and kidney should also be included. Aerobic culture will be performed. NOTE: Submit all fresh tissues individually in either a Whirlpak bag or Ziplock bag.

7. Collect a sample for parasitology. Fecal material should be collected in a plastic vial for subsequent Cryptosporidium exam.

Cryptosporidium

Cryptosporidiosis in Bovine and Human Health:

Crypto-sporidium parvum is highly infectious and highly resistant to inactivation in the environment. There is no routinely successful form of therapy available. There is also a zoonotic implication in humans handling the animals, especially in immunocompromised humans.

Etiology and Pathogenesis: Neonatal calf diarrhea usually involves the association of more than one pathogen. The most common implicated pathogens are E. coli, rotavirus, coronavirus, and Cryptosporidium parvum.Cryptosporidium parvum (disease name Crypto-sporidiosis) is a protozoan parasite transmitted by fecal-oral contamination. These protozoa invade the apical surface (brush border) of the enterocyte in the distal small intestine and proximal colon and form parasitophorus vacuoles where development occurs. Infection results in crypt and submucosal inflammation, necrosis of microvilli, villous atrophy, and decreased mucosal enzyme activity. This results in decreased absorptive ability of the intestinal tract, fermentation of nutrients within the lumen, and osmotic diarrhea.

Life cycle: Infection begins by ingestion of oocysts from feces. These oocysts contain four sporozoites and initiate infection following excystation. The organism replicates asexually and then sexually to produce new oocysts that are shed into the environment in feces or reinfect the host. The definitive hosts include many mammals such as cattle, dogs, cats, and humans.

Epidemiology: C. parvum oocysts are commonly found in the feces of healthy calves. The cause of diarrhea depends on multiple factors such as the degree of virulence of the pathogenic strain, the presence of more than one pathologic agent, and the success of passive transfer of colostral immunoglobulins. Calves with low immunity are highly susceptible to enteropathogenic infections leading to severe and often fatal diarrhea. Also, the lack of specific antibodies in the dam and the use of specific vaccines may interfere in the immunoglobulin transfer to the calf. Stress factors, poor environmental conditions, exposure to contaminated maternal feces as well as feces from healthy calves, and inappropriate diet also increase the risk for disease. Transmission is by fecal-oral contact and fecal aerosol.

Diagnostics: Fecal samples from untreated calves should be submitted during early diarrheic stages. Sugar flotation can be performed to identify the oocysts. Bacteriology and virology cultures can be performed to verify the presence of other agents. The microbiologic interpretation may be difficult because of mixed infection and because some potential enteropathogens are commonly present in healthy calves. Ideally, live representative calves should be presented for necropsy examination so that fresh intestinal sections can be prepared to identify the presence of organisms at the surface of epithelial cells.

Treatment: There is no effective chemo-therapeutic agent for routine treatment of cryptosporidiosis, but supportive care is recommended. Paromycin has been used with limited success in cats and human patients, but its efficacy in other species has not been determined. Oral Bovine Serum concentrate has been used in calves with experimentally induced cryptosporidiosis. Hunt and Armstrong determined that there was a 33% reduction in the volume of diarrhea at the peak of illness, 30% reduction in intestinal permeability, and enhanced ideal crypt depth and villous surface area, as compared to untreated, infected calves.

Prevention and control: Good hygiene during management of the entire herd is important in reducing the incidence of cryptosporidiosis. Isolation of sick calves to a separate area to reduce contamination is also important. The dam and calf should be provided good nutrition, and administration of high quality colostrum within the first six hours of birth helps reduce infection.