VMD 411: Veterinary Clinical Medicine-I (General and Systemic) (2+1)

TOXEMIA

• Toxemia is a generic term for the presence of toxins in the blood. It is not necessarily the same as Bacteremia.
• The toxins released by bacteria can enter the blood stream and can move throughout the body without any bacteria entering the blood stream.
• Pre-eclampsia, a serious condition in pregnancy that involves hypertension and proteinuria, may be caused by toxemia.

Septicemic Disease (Colisepticemia)

• Septicemia caused by Escherichia coli is a common disease of calves, and to a lesser extent lambs, <1 wk old.
• It may present with signs of acute septicemia or as a chronic bacteremia with localization.
• The disease is caused by specific serotypes of E coli that possess virulence factors enabling them to cross mucosal surfaces and produce bacteremia and septicemia.
• However, the main determinant of the disease is deficiency of circulating immunoglobulins as the result of a failure in passive transfer of colostral immunoglobulin; septicemic disease due to invasion by E coli occurs only in immunoglobulin-deficient calves.
• Colisepticemia is seen during the first week of life, most commonly at 2-5 days of age.
• Chronic disease with localization can be seen up to 2 wk of age. The disease is usually sporadic and is more common in dairy than beef calves.

Transmission and Pathogenesis

• Invasion occurs primarily through the nasal and oropharyngeal mucosa but can also occur across the intestine or via the umbilicus and umbilical veins.
• There is a period of subclinical bacteremia that, with virulent strains, is followed by rapid development of septicemia and death from endotoxemic shock.
• A more prolonged course, with localization of infection, polyarthritis, meningitis, and less commonly uveitis and nephritis, is seen with less virulent strains.
• Chronic disease also develops in calves that have acquired marginal levels of circulating immunoglobulin.
• The organism is excreted in nasal and oral secretions, urine, and feces; excretion begins during the preclinical bacteremic stage.
• Initial infection can be acquired from a contaminated environment.
• In groups of calves, transmission is by direct nose-to-nose contact, urinary and respiratory aerosols, or as the result of navel-sucking or fecal-oral contact.

Clinical Findings and Diagnosis

• In the acute disease, the clinical course is short (3-8 hr), and signs are related to the development of septic shock.
• Pyrexia is not prominent, and the rectal temperature may be subnormal.
• Listlessness and an early loss of interest in sucking are followed by depression, poor response to external stimuli, collapse, recumbency, and coma.
• Tachycardia, a poor pulse pressure, and a prolonged capillary refill time are seen.
• The feces are loose and mucoid, but severe diarrhea is not seen in uncomplicated cases.
• Mortality approaches 100%. With a more prolonged clinical course, the infection may localize.
• Polyarthritis and meningitis are common; tremor, hyperesthesia, opisthotonos, and convulsions are seen occasionally, but stupor and coma are more common.
• A moderate but significant leukocytosis and neutrophilia are seen early, but leukopenia is marked in the terminal stages.
• The joint fluid contains increased inflammatory cells and protein, and the CSF shows pleocytosis and an increased protein concentration; organisms may be evident on microscopic examination.
• Less commonly, other bacteria, including other Enterobacteriaceae, Streptococcus spp , and Pasteurella spp , produce septicemic disease in young calves.
• These organisms are more common in sporadic cases than as causes of outbreaks.
• They produce similar clinical disease, but they can be differentiated by culture.
• As with colisepticemia, the primary determinant of these infections is a failure of passive transfer of immunoglobulins.
• The diagnosis is based on history and clinical findings, demonstration of a severe deficiency of circulating IgG, and ultimately, demonstration of the organism in the blood or tissues.
• Zinc sulfate or total protein estimation can be used for rapid estimation of IgG ( Nutritional Requirements).

Treatment

• Treatment requires aggressive use of antibiotics.
• Because there is no time for sensitivity testing, the initial choice should be a bactericidal drug that has a high probability of efficacy against gram-negative organisms.
• Antibacterial therapy should be coupled with aggressive fluid, drug, and other therapy for endotoxic shock. Mortality is high despite aggressive treatment.

Control and Prevention

• Calves that acquire adequate concentrations of immunoglobulin from colostrum are resistant to colisepticemia.
• Therefore, prevention depends primarily on management practices that ensure an adequate and early intake of colostrum.
• The adequacy of the farm’s practice of feeding colostrum should be monitored, and corrective strategies applied as required.
• In dairy herds, natural sucking does not guarantee adequate concentrations of circulating immunoglobulins, and calves should be fed 2-4 L of first-milking colostrum, using a nipple bottle or an esophageal feeder, within 2 hr of birth, followed by a second feeding at 12 hr.
• The circulating concentration of immunoglobulin required to protect against colisepticemia is low; however, high concentrations of circulating immunoglobulins are desirable because they decrease susceptibility to other neonatal infectious diseases.
• When natural colostrum is not available for a newborn calf, commercial colostrum substitutes containing 25 g IgG will provide sufficient immunoglobulin for protection against colisepticemia if fed early in the absorptive period.
• Plasma containing at least 4 g and preferably 8 g IgG, administered parenterally, will provide some protection for older calves that have not been fed colostrum and are unable to absorb immunoglobulins from the intestine.
• Small-volume hyperimmune serum is of benefit only when it contains antibody specific to the particular serotype associated with an outbreak.
• The risk of early infection should be minimized by hygiene in the calving area and disinfection of the navel at birth.
• To minimize transmission, calves reared indoors should be in separate pens (without contact) or reared in calf hutches.