CALF DIARRHOEA – IMPORTANT DISEASE OF NEONATAL CALF MORTALITY IN INDIA

Diseases of the neonatal calf and related mortality is major cause of economic losses in animal husbandry. Among these, diarrhoea is one the most common diseases reported in calves up to 3 months old. Calf diarrhoea (scouring) is a multi-causative disease that can result in serious financial and animal welfare implications during early period of life. Calf diarrhoea is attributed to both infectious (viral, bacterial, protozoa) and non-infectious factors. The environment and management practices, mineral imbalances also influence disease severity or the outcome of calf diarrhoea. The multifactorial complexities of calf diarrhoea makes the disease difficult to control effectively in modern husbandry practices.Acute diarrhoea in calves is responsible for major cause of deaths in dairy husbandry during the pre-weaning period. Calf mortality during early 1-2 months may vary from 10-30% and 60% of these results from calf diarrhoea. The economic losses occur not only from mortality but also from treatment costs and time spent on care as well as subsequent chronic ill thrift and impaired growth performance. Calf diarrhoea is often recognized by passage of soft fluid to watery or sometimes bloody faeces, abnormal colour, rapid body weight loss and metabolic changes due to dehydration and electrolyte loss. The presented article aims to bring awareness about calf diarrhoea, its possible causative agents and factors and preventive measures.

Causal agents:

Calf diarrhoea during early life results mostly from infectious origin. Before parturition growing foetus is protected in near sterile, climate controlled environment of the dam’s womb. Immediately after birth the calf is exposed to heavy environmental pathogens and extremes of climatic situations and responds differently depending upon the vigor, passive and maternal immunity, management practices and genetic resistance. The causative pathogens can be primary agents which may be bacterial, viral or protozoal pathogens or many may act as secondary agents to amplify the deteriorating changes in the system. Most common causative agents in calf diarrhoea during early 3 months of life has been implicate to enteropathogenic Escherichia coli, rotavirus, coronavirus, salmonella species, cryptosporidium, coccidia, clostridium and few newly emerging enteric pathogens such as bovine torovirus and caliciviruses (bovine norovirus and nebovirus).Inclement weather conditions such as low or high temperatures, heavy rain, wind and high moisture may act as stress factors to young calves and increase the susceptibility of calves to diarrhoea. There is also seasonal variation related to colostrum uptake by calf intestine. Early immunity in neonatal calves depends almost entirely on antibodies ingested through the colostrum intake. Colostrum taken after 72hrs provides local protection in the gastrointestinal tract against potential infectious agents. Failure of passive transfer of immunoglobulins through inadequate intake of colostrum predisposes the neonates to gastrointestinal and systemic infections.Passive transfer is influenced by the concentration of colostral immunoglobulins, the volume of colostrum intake and the time passed by after birth. Larger herd size is associated with an increased incidence of calf diarrhoea attributed to favourable chance of transmission. The seasonal variation of rotavirus diarrhoea in India varies in different geographical regions with high incidence in winter months at low relative humidity in north India.

Table 1: Causative agents of calf diarrhoea and its epidemiology

Causative agent Susceptible age Characteristic symptoms Transmission

Enterotoxigenic (K99-bearing) E coli < 3-5 days old Non-inflammatory secretory diarrhoea with Profuse amounts of liquid feces passed, and the calves rapidly become depressed and recumbent. Fecal-oral route

Salmonella sp 2–12 week of life, generally within 14 days of life Feces that are foul smelling and contain blood, fibrin, and copious amounts of mucus. Septicemia, with high fever and depression progressing to prostration and coma, is the salient manifestation of salmonellosis Fecal-oral route, but may also through contaminated saliva, milk/colostrum

Clostridium perfringens Few days old and upto 8 weeks fatal hemorrhagic enteritis, abdominal pain, and death within a few hours Fecal-oral route

Rotavirus 5–15 days old but can affect calves up to several months of age Mal absorption diarrhoea; Feces are voluminous, soft to liquid, and often contain large amounts of mucus. Affected calves are only moderately depressed and often continue to suck or drink milk. Fecal-oral route, fecal aerosol

Coronavirus 1 to 2 weeks of age Causes profuse watery diarrhoea with mucus. Affected calves will become dehydrated very quickly and will develop a fever and loss of appetite Fecal-oral route, respiratory aerosol.

Cryptosporidium parvum 5–35 days old but most commonly in the second week of life. persistent diarrhoea that does not respond to therapy, hypoglycemia Fecal-oral route, dust in the air

Giardia duodenalis Any age more common in 1 and 3 weeks of age Associated with chronic mucoid diarrhoea Fecal-oral route

Dietary diarrhoea weeks old Voluminous feces of pasty to gelatinous consistency. –

Pathogenesis of calf diarrhoea:

Scour occurs when the intestine does not complete absorption of electrolytes and water from luminal contents in gastro-intestinal tract. Calf diarrhoea depending on the causal agents occurs due to following pathological events:

• Secretory diarrhoea: It occurs due to abnormal amount of fluid is secreted into the gut, exceeding the resorptive capacity of the intestinal mucosa impaired fluid and electrolyte absorption by gastro-intestinal tract. It may result either frombacterial toxins produced by pathogenic bacteria or reduced absorptive surface area due to bile acids, laxatives, circulating hormones (histamine), drugs (chloramphenicol, neomycin, or tetracycline) and poisons in intestine. Most cases of acute and chronic diarrhoea are due to this mechanism.

• Malabsorption or Exudative diarrhoea: Destruction of mature enterocytes and/or activation of the enteric nervous system by vasoactive components from the damaged cells and secretion of a viral enterotoxin account for maldigestive/malabsorptive diarrhoea. This occurs due to impaired capacity of the mucosa to absorb fluid and nutrients.Malabsorptive diarrhoea may be aggravated by the colonic fermentation of nutrients such as lactic acid and which acts as osmotically active substances and further aggravates the condition. Dietary diarrhoea generally results from osmotic diarrhoea due to malabsorption.

Irrespective of mode of pathogenesis, calf suffers from net loss of water, sodium, potassium, and bicarbonate. In severe diarrhoea, the calf may develop hypovolemia, hyponatremia, acidemia, hypoglycemia and pre-renal azotemia.It may result in body weakness and septicemia.

Treatment strategies in calf diarrhoea aims to maintain and restore fluid and electrolyte losses in the body based on extent of dehydration and electrolyte imbalance, correction of acid- base disturbances (in general acidosis)alternation in diet, and eliminate source of infection by antimicrobials and herbal antidiarrhoeal.

Fluid therapy: Fluid therapy should be initiated as soon as possible regardless of evidence of clinical symptoms of dehydration in calf suffering from diarrhoea. Fluid therapy can be given either as oral fluid rehydration or by intravenous route. The choice depends on severity of dehydration, physical vigor of affected calf, palpebral reflex, body weight loss and acidosis. Generally dehydration in calves can be assessed using skin tent test as indicated below in table 2.

Table 2: Assessment of dehydration in calf

Parameters Dehydration

Skin “tents” for 4 seconds or less, standing calf: less than 5 % of body weight

Skin “tents” persisting for 5seconds, calf lying down upright Upto 7% of body weight

Skin “tents” persisting for more than 5seconds, calf lying down flat Severe dehydration upto 9% of body weight