Equine Medical Guidelines – foal diseases

Normal Vital Signs

Age	Temp	Pulse	Resp	Behavior
0-1min	37.5	70-80	70	Breaks amnion by limb/head movement
2-30 mins	37.8	120-140	50	Cord rupture, shivering, sternal, sucking movements, attempts to stand
1-12h	37.8	140-150	40	Standing, nursing, passes meconium and urine
12-18h	37.8	110-120	35
24-48h	37.8	90-100	30
48-72h	37.8	60-80	20

Foal diarrhoea

Common causes

Cause	Age group affected	Notes	Antimicrobial choice
Foal heat diarrhea (coprophagy)	5-14 days	Foals clinically well, no fever	None
Rotavirus	3-10 days	Often dehydrate rapidly (malabsorptive diarrhoea)	Prophylactic antimicrobials to reduce the risk of sepsis. See below.
Coronavirus			Prophylactic antimicrobials to reduce the risk of sepsis. See below.
Salmonella	Any age	*Zoonoses	Prophylactic antimicrobials to reduce the risk of sepsis. See below.
Endotoxaemia	Any age	Foals with endotoxaemia due to sepsis or other conditions commonly have diarrhoea.	Treat sepsis, or other cause of endotoxaemia.
Cryptosporidium	5-21 days	*Zoonoses Often self-limiting	None
Rhodococcus equi	4-16 weeks	~75% of foals with respiratory R. equi will have extrapulmonary lesions, of which the GI is most common (33%)72.	Clarithromycin & rifampin73
Clostridium spp	Most common in very young foals, can occur at any age, especially associated with antimicrobial therapy		Metronidazole
Parasites –       Strongyloides westeri (Threadworm) –       Parascaris equorum (Round worm)	<14 days   Infection from birth, clinical signs from 4-5 months of age	Uncommon   Usually other signs of ill-thrift are present.	None

TREATMENT

Prophylactic antimicrobial choice for neonatal foals with diarrhoea: broad spectrum coverage is required as sepsis in foals commonly involves either Gram positive or Gram negative pathogens⁷⁴. In foals that are dehydrated and azotaemic, avoid nephrotoxic drugs such as gentamicin and oxytetracycline. Intravenous trimethoprim / sulphonamide is recommended in these cases.

In foals with normal hydration status, penicillin in combination with gentamicin, or trimethoprim / sulphonamide is recommended.

Neonatal encephalopathy

Foals born with neonatal encephalopathy are at high risk for sepsis as they often have failure of passive transfer, or failure to absorb antibodies even when colostrum is consumed in sufficient quantities. In addition, these foals are often recumbent and have higher exposure to environmental pathogens.

Prophylactic antimicrobial therapy is recommended. Broad spectrum coverage is required as sepsis in foals commonly involves either Gram positive or Gram negative pathogens⁷⁴. In foals that are dehydrated and azotaemic, avoid nephrotoxic drugs such as gentamicin and oxytetracycline. Intravenous trimethoprim / sulphonamide is recommended in these cases.

In foals with normal hydration status, penicillin in combination with gentamicin, or trimethoprim sulphonamide is recommended.

Foal pneumonia

Foal typically suffer from pneumonia not as neonates but at 1-4 months of age.

Streptococcus zooepidemicus and Rhodococcus equi are the most common pathogens and occur with equal frequency in most parts of Australia. Pneumonia because of these pathogens is impossible to differentiate clinically. Trans-tracheal wash is highly recommended.

Common pathogens	Antimicrobial recommendation	Duration of therapy
Streptococcus zooepidemicus	Penicillin IM or IV	Typically 1 week
Rhodococcus equi	Clarithromycin and rifampin	Typically 4-6 weeks

Note. There has been some recent controversy over the use of rifampin in combination with macrolides due to the findings of some studies which show reduced plasma concentrations of macrolides. However, there is also evidence to support combination therapy. The combination is still preferred as it may reduce the emergence of resistance, there is no evidence of superiority of macrolide therapy alone in clinical studies and there is no patient based studies indicating a detrimental effect of combination therapy.

DURATION OF THERAPY

Treat until clinical signs, haematological and diagnostic imaging abnormalities have resolved.

More information about R.equi can be found in the ACVIM consensus statement on Diagnosis, Treatment, Control, and Prevention of Infections Caused by Rhodococcus equi in Foals

Neonatal sepsis

DIAGNOSTICS

Sepsis score can be used to assess risk (see website). Blood for culture and susceptibility should be collected but false negatives are common.

TREATMENT

Based on culture and susceptibility results if possible. Empiric therapy can be initiated while results pending.

Penicillin & gentamicin is recommended. Care with gentamicin if renal function is compromised. Intravenous trimethoprim / sulphonamide is alternate.

DURATION OF THERAPY

2 weeks is generally considered to be adequate, unless focal infection develops (i.e. septic arthritis).

Septic synovial structures

DIAGNOSTICS

Arthrocentesis should be performed to obtain fluid for cytological evaluation and for culture and susceptibility testing in all cases. Radiographs should be taken to investigate bone involvement. Ultrasound examination of the umbilical remnants should also be performed as this may be the source of the bacteraemia.

TREATMENT

Based on culture and susceptibility results. Empiric therapy can be initiated while results pending. Penicillin & gentamicin is recommended. Oxytetracycline is an alternative, especially if osteomyelitis is diagnosed.

DURATION OF THERAPY

Treat for 1 week past resolution of clinical signs, longer if osteomyelitis is present.

Patent urachus

DIAGNOSTICS

Ultrasound evaluation should be performed to rule out omphalophlebitis. If no enlargement of the umbilical remnants is identified antimicrobial therapy is not indicated.

TREATMENT

No antimicrobial therapy indicated.

Frequent topical antibacterial therapy with chlorhexidine is recommended until patency resolves.

Omphalophlebitis (navel ill)

DIAGNOSTICS

Ultrasound evaluation should be performed to define the infected structure and to allow for monitoring with treatment. Monitor closely for development of septic synovial structures.

TREATMENT

Penicillin & gentamicin is most effective but often not tolerated well. Trimethoprim / sulphonamide or doxycycline are suitable alternatives that can be given orally. Surgical excision can be considered, surgical site infections are common post-operatively.

DURATION OF THERAPY

Serial ultrasonographic examination should be performed and therapy continued until 1 week after resolution of disease.

High risk foals

Premature foal and those with neonatal encephalopathy (’Dummy Foal Syndrome’) are at increased risk of sepsis.  Failure of passive transfer should be addressed with plasma transfusion. There is no evidence for any benefit from prophylactic antimicrobials in place of plasma transfusion.

DIAGNOSTICS

Serial haematologic evaluation and sepsis score may guide necessity for antimicrobial therapy.

TREATMENT

Prophylactic therapy is warranted when leukopaenia is present or sepsis score is high. Penicillin & gentamicin is most appropriate but care should be taken in foals with impaired renal function. Trimethoprim / sulphonamide IV is an alternative.