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haematuria. The diagnosis can be confirmed by a declining packed cell volume. Serum chemistry should be tested to evaluate for common complications such as kernicterus, hepatic failure or acute kidney injury. An affected foal should be muzzled or separated from the mare for 24 h, kept in a quiet environment, and carefully monitored. It is essential to maintain adequate hydration and to limit stress to the foal. The mare should be milked, and the milk discarded. Most foals will recover if stress is kept to a minimum. Foals with more severe anaemia (packed cell volume <12%, haemoglobin <50 mg/l) may require transfusion which can be difficult in the field. The mare is the best source of red blood cells, but attempts to wash red blood cells without a centrifuge can be challenging and time-consuming. If no other option is available, a blood transfusion from an unrelated gelding may be life-saving. Between 1 and 2 l of blood is collected into acid citrate dextrose anticoagulant and administered over 2–4h. Antibiotic coverage is usually indicated as the foal is at risk for sepsis due to systemic compromise. Prevention is much more effective than treatment. At-risk mares may be screened during the last month of gestation for presence of red cell alloantibodies. Colostrum from positive mares should be discarded, and the foal should be provided with an alternative source of colostrum (Sellon 2006).
Sepsis Signs of sepsis are nonspecific and include decreased nursing, depression progressing to recumbency, injected mucous membranes, and petechia on mucous membranes and inside of the ears; these signs represent the development of the systemic inflammatory response syndrome. The syndrome in neonates has been defined as alterations in at least three of the following parameters (one of which must be abnormal temperature or leucocyte count): body temperature >39.2°C or <37.2°C; heart rate >115 beats/min; respiratory function >56 breaths/min; peripheral white counts (white blood cell count 9 109/l) >14.4 or <6.9 or >5% band neutrophils; venous blood lactate >5.0 mmol/l; and venous blood glucose <2.8 mmol/l (Fielding and Magdesian 2015; Wong and Wilkins 2015). Historical factors such placentitis, premature lactation, mare vulvar discharge, prematurity and FPT contribute to a suspicion of sepsis. Early recognition and treatment of sepsis is
TABLE 3: Common antibiotics used in foals Antimicrobial Amikacin
Ampicillin Na Cefotaxime Ceftazidime Ceftiofur
Chloramphenicol* Gentamicin
Metronidazole Oxytetracycline Potassium penicillin
associated with a better outcome and has led to the development of scoring systems as an aid to identification of infected foals. Examples of sepsis score worksheets are published in various places (Brewer and Koterba 1988; Brewer 1990; Corley and Furr 2003; Weber et al. 2015). Foals with suspected sepsis should be referred to a hospital, but if this is not possible, then cardiovascular support, good nursing care and antibiotics should be instituted (Table 3). The distribution and metabolism of drugs is expected to
be different in foals as compared to mature horses because of a higher percentage of body water, decreased protein binding of drugs, and immature metabolism and excretion of drugs by the liver and kidney (Magdesian 2003). Prior to initiating antibiotic therapy, a sterile blood culture should be obtained to direct antibiotic selection. In lieu of culture and sensitivity information, empirical broad-spectrum antibiotic therapy should be employed. The initial treatment of a suspected septic foal with normal renal function should include a b-lactam drug and an aminoglycoside. Aminoglycosides carry the potential for nephrotoxicity; however, it is unlikely that peak and trough aminoglycoside levels can be measured in the field. Without therapeutic drug monitoring, efforts to maintain hydration, monitor urinalysis and determine serum creatinine concentration at least weekly are recommended to prevent adverse effects on the kidneys (Vaala et al. 2009). If renal function is abnormal or suspect, then antibiotic choices should be high-dose ceftiofur, trimethoprim-sulfonamides, ticarcillin/clavulanic acid or a third-generation cephalosporin. Clinical experience may dictate antimicrobials that are more likely to be effective in a given area (Sanchez 2005; Russell et al. 2008). The intravenous route is ideal in foals aged <7 days, but the
intramuscular route may be used in a field setting. Bacteraemic foals without localising signs should be treated for at least 10–14 days. If antibiotics are used prophylactically, treatment for 3–5 days is recommended (Axon and Wilkins 2015). When localising signs are present, treatment should continue until all signs of infection are resolved, and temperature, complete blood cell count, fibrinogen, and serum amyloid A are returned to normal values for 72 h. A follow-up complete blood cell count and fibrinogen are recommended 1 week after therapy is discontinued to
Dose
Notes
20–30 mg/kg bwt i.v. or i.m. q. 24 h May cause renal damage, Gram -ve coverage only 20 mg/kg bwt i.v. q. 6 h 40 mg/kg i.v. q. 6 h
Usually used with aminoglycoside 40–50 mg/kg bwt i.v. q. 6 h
Used only when resistance to commonly used antibiotics is identified Used only when resistance to commonly used antibiotics is identified
5–10 mg/kg bwt i.v. or i.m. q. 6–12 h Used alone or in combination with aminoglycoside 40 mg/kg bwt/per os q. 6 h 8–15 mg/kg i.v. or i.m. q. 24 h
Wear gloves as there is a human health risk
10 mg/kg bwt per os, i.v., or per rectum q. 12 h 2 g/50 kg foal
5 mg/kg bwt i.v. q. 12 h 22,000 units/kg bwt i.v. q. 6 h
May cause renal damage, Gram -ve coverage only Used most commonly for suspected clostridial infections
For treatment of contracted tendons. Do not give to dehydrated foals as may cause renal injury. Repeat q. 24–48 h. May be useful for osseous infection
Used in combination with an aminoglycoside
Ticarcillin/clavulinic acid 40–50 mg/kg bwt i.v. or i.m. q. 8 h For use in b-lactamase producing bacteria Trimethoprim-sulfonamide 15 mg/kg bwt/per os q. 12 h
* Use of this antibiotic may be restricted or prohibited in some countries. © 2016 EVJ Ltd Used for long-term treatment in foals with demonstrated susceptibility
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