Introduction
Despite increasingly precise knowledge, neonatal calf diarrhea (NCD) remains the leading cause of death among young calves, both in dairy and beef cattle farms.
Beyond the health issue, this disease, which occurs within the first month of a calf’s life, is primarily an economic problem that significantly impacts the financial balance of farms:
Diarrhea causes a loss of water and electrolytes and leads to dehydration & energy loss.
Multifactorial, yet always the same predisposing factors.
The main sources of the germs involved are
I. Etiology
While the diagnosis is straightforward (liquid stools, varying degrees of shock, etc.), identifying the exact cause based solely on clinical signs is difficult. Laboratory analysis is often required to confirm the causative agents.
However, based on the farm’s history, the age of the calves, and the physical appearance of the diarrhea, it is possible to make suspicions or direct towards a potential etiology.
- 45 to 50% of diarrhea cases are due to :
- Rotavirus, Coronavirus, Torovirus
They cause morphological and functional alterations in enterocytes, leading to the proliferation of resident bacterial flora and a digestive malabsorption syndrome. This infection results in the loss of water and ions, as well as the fermentation of lactose in the large intestine, producing acids (D-lactic acid, short-chain fatty acids). These acids are partially absorbed into the bloodstream, leading to acidosis.
- 30 to 35% of diarrhea cases are due to :
- E. Coli (often underdiagnosed; ELISA K99 test)
This causes diarrhea through hypersecretion or secretion due to toxin activity. This includes salmonella and enterotoxigenic E. coli. These toxins do not cause cellular lesions but promote instead the secretion of ions and, therefore, water.
- Salmonella spp
- Campylobacter
- Clostridium perfingrens type C
- 20 to 25% of diarrhea cases are due to Protozoa :
- Cryptosporidia (Cryptospridium parvum)
- Coccidia (Eimeria spp)
Classification of Rotaviruses
- 7 serogroups (A to G)
- 98% of rotaviruses belong to group A.
- Cross-protection
- 8 serotypes
- G6 is predominant (> 66% in F and GB)
Classification of coronaviruses
- BCoV belongs to the Betacoronavirus genus (closely related to the SARS-CoV and MERS-CoV human viruses).
- There is only one serotype, but there are antigenic differences between the different strains, which may explain short-lasting protective immunity.
Classification of Escherichia coli
- Serological classification based on structural antigens
- O antigen present in the bacterial envelope (“LPS”)
- H antigen present in the flagella
- K antigen present in the capsule
=> Bacterial identity card (epidemiological interest)
Classification by the pathogenicity of the bacteria
- Local action => Cytotonic effect => The enterocytes are not damaged
- ETEC for EnteroToxigenic E. Coli
- F5 (K99) / F17 (FY) or F41
- Local and systemic action => Cytotoxic effect
- EPEC for EnteroPathogenic E. Coli
- VETC for VeroToxigenic E. Coli
- EPEC sans toxine (dommage local)
- EPEC without toxin (local damage)
- Invasive strain => sepsis or enterotoxin-like pathology
- NTEC for NecroToxigenic E. Coli
- NB one of the most common attachment factors is CS31A, but also FY(F17)
- Hemorrhagic colitis and sepsis
- Special case GEP (Paralyzing Gastroenteritis)
Helps in the diagnosis of neonatal diarrhea
Diarrhea and calf age
According to Pr Yves Millemann
Diarrhea based on etiology
II. Pathophysiology of diarrhea
Secretory diarrhea
Typically veal less than a week old
ETEC attachment => production of enterotoxins => ↗ Secretions => accumulation of ions (Na+ and Cl- in the intestinal lumen => call for water in the lumen => very liquid DIARRHEA with rapid dehydration
Osmotic diarrhea with malabsorption syndrome
Typically calves aged 2-3 weeks
Multiplication of Rotavirus, Coronavirus and/or Cryptosporidia in the wall of enterocytes => Destruction of villi mainly in the upper part of the TD => proliferation of the resident flora of EColi => ↘ Absorption => DIARRHEA rather pasty
Malabsorption syndrome (Lactose and lipids) is due to the alteration of the apical membrane of enterocytes => reduction of brush border enzymes including lactase => arrival of undigested lactose in the colon => fermentation by the colonic flora +> reduction of apical co-transport Na+ /AA and Na+ /Oses
Septicemic form
This set of disturbances creates, especially since the treatment was late, a strong inflammation of the wall which can lead to bacteremia by translocation of bacteria from the digestive tract => septicemia => main risk of mortality
The population at risk are calves less than 7 days old without colostrum or with poor transfer of passive immunity
Whatever the origin of the diarrhea, it results in dehydration through loss of water and metabolic acidosis.
III. Treatment of diarrhea
A – Nursing
- Preventing hypothermia
- Feeding the calf
B – Fluid therapy
No dehydration or mild dehydration = HP loss < 5%
- Continue breastfeeding: source of energy
- Oral rehydration at the first signs of diarrhea, with a buffered solution with a high SID
- This rehydrating solution must be distributed away from milk feeding.
- A high SID allows rapid correction of acidosis as well as treatment of electrolyte leakage
Severe dehydration = 5 to 8% of PV
- Same unless the sucking reflex has disappeared => use of a solution rich in energy and electrolytes by IV route
Very severe dehydration = PV loss > 8%
- Slow infusion of at least 4 liters of solution
- Plus oral route respecting a delay of 8-12 hours between the infusion and the oral solution
