Clinical findings in 10 foals with bacterial meningoencephalitis J. VIU, L. MONREAL, E. JOSE-CUNILLERAS, C. CESARINI, S. AÑOR † and L. ARMENGOU* Servei de Medicina Interna Equina, Facultat de Veterinària, Universitat Autònoma de Barcelona, Barcelona, Spain † Servei de Neurologia i Neurocirurgia, Facultat de Veterinària, Universitat Autònoma de Barcelona, Barcelona, Spain. *Correspondence email: lara.armengou@uab.es; Received: 10.01.11; Accepted: 26.07.11 Summary Reasons for performing the study: Bacterial meningoencephalitis is a severe complication in septic foals and there is scarce and often unclear information in the equine literature. Objectives: To report the most frequent clinical signs, clinicopathological findings, causative agents, treatments given and outcome of a group of foals with confirmed bacterial meningoencephalitis. Methods: Foals aged <6 months of age admitted to the Universitat Autonoma de Barcelona (2004–2009) with confirmed bacterial meningoencephalitis were retrospectively included in the study. Diagnosis of bacterial meningoencephalitis was made by cerebrospinal fluid (CSF) culture, CSF analysis consistent with bacterial infection, observation of bacteria in CSF cytology or post mortem confirmation. Results: Nine neonates and one 5-month-old foal were included. The most frequently observed clinical signs were alterations in mental status (10/10), recumbency (8/10), weakness (8/10), abnormal pupillary light reflexes (6/10), decreased suckling-reflex (6/9), seizures and/or nystagmus (4/10). Common clinicopathological alterations included hyperfibrinogenaemia (8/9), hyperlactataemia (7/7), and neutropenia (5/10) or neutrophilia (5/10). Most neonates (8/9) developed bacterial meningoencephalitis despite having a sepsis score near the cut-off value (median = 12). On CSF analysis, pleocytosis (9/9), increased total protein concentration (5/6) and intracellular bacteria (6/9) were detected. The most frequently isolated bacterium was Escherichia coli. Once bacterial meningoencephalitis was diagnosed, antimicrobial therapy was switched to third and fourth generation cephalosporins. Conclusions: The diagnosis of bacterial meningoencephalitis is established based on CSF analysis and culture. Clinical recognition of bacterial meningoencephalitis is difficult and can be easily overlooked. Moreover, severe sepsis is not necessary to develop bacterial meningoencephalitis. Potential relevance: CSF analysis should be considered more often in sick newborn foals with signs indicative of central nervous system (CNS) involvement. Cerebrospinal fluid (CSF) cytology and culture would help to confirm or rule out unnoticed bacterial meningoencephalitis, and to choose appropriate antimicrobial therapy. Keywords: horse; neonate; septic meningitis; sepsis; neurological disease Introduction Bacterial infection of the equine central nervous system (CNS) is an uncommon condition and has been reported to affect 2.5% of horses with neurological disease (Furr 2008). Bacterial meningoencephalitis appears to be more frequent in neonatal foals. It is reported as a complication of sepsis in as many as 8–10% of septic foals (Koterba et al. 1984; Brewer and Koterba 1990) and is associated with a high mortality rates (Koterba et al. 1984; Brewer and Koterba 1990; Sanchez et al. 2008). However, information about bacterial meningoencephalitis in equine patients is scarce, and some authors consider that there is a lack of comprehensive case series of bacterial meningitis in these animals (Mitchell et al. 2007). Reported clinical signs of bacterial meningoencephalitis, such as lethargy, weakness, fever and seizures (Pellegrini-Masini and Livesey 2006; Furr 2008) are nonspecific and frequently present in other common neonatal diseases. Early diagnosis of bacterial meningoencephalitis is essential for selection of appropriate therapy, and for increasing the likelihood of survival. However, clinical signs consistent with bacterial meningoencephalitis are often observed in many critically ill foals with other diseases, such as hypoxic-ischaemic encephalopathy (HIE). Thus, recognition of bacterial meningoencephalitis based on clinical signs can be difficult. In human medicine, it is well known that meningitis can easily go unrecognised in septic neonates, so cerebrospinal fluid (CSF) is routinely collected in septic infants (Heath et al. 2003). The objective of this retrospective case series was to review the clinical signs, causative agents, laboratory findings and outcome in foals with confirmed bacterial meningoencephalitis admitted to a referral equine hospital. Materials and methods Case selection Data from medical records of all newborn foals (<21 days old) and foals aged 21 days to 6 months, admitted to the Universitat Autonoma de Barcelona from January 2004 to December 2009, with a confirmed diagnosis of bacterial meningoencephalitis were reviewed. Diagnosis of bacterial meningoencephalitis was confirmed by a board-certified neurologist and was based on either bacterial growth on CSF culture, consistent CSF analysis, or post mortem confirmation. Cerebrospinal fluid (CSF) analysis was considered consistent with bacterial meningoencephalitis when neutrophilic pleocytosis or intracellular bacteria were detected. Post mortem diagnosis was reached by the presence of either purulent CSF or histopathological evidence of bacterial infection in the CNS. Moreover, diagnosis of sepsis in newborn foals was reached when at least one of the following conditions occurred: positive blood culture, increased sepsis score (>11) or post mortem findings consistent with sepsis. Medical record review Data obtained from medical records included case details, clinical signs, neurological and ophthalmological examination findings (confirmed by a boarded neurologist and ophthalmologist, respectively), and clinicopathological results obtained when clinical signs consistent with bacterial meningoencephalitis were detected (total white blood cell count, neutrophil count, packed cell volume; total plasma protein [TP], fibrinogen, lactate, sodium, potassium and chloride concentrations; serum IgG concentration; CSF total protein concentration, cell count and cytology; and blood and CSF cultures). Other information included was: sepsis score (neonatal foals) (Brewer and Koterba 1988), concurrent diseases during hospitalisation, treatments given, outcome (survival to discharge from the hospital, euthanasia or death due to complications from sepsis or bacterial meningoencephalitis), and post mortem findings. Information regarding the organisms isolated from blood and CSF samples, including bacterial identification and antimicrobial sensitivity, was also obtained. Results Nine of 173 septic newborn foals (from a total of 309 sick neonates admitted during the study period) fulfilled the inclusion criteria (Foals 1–9). In addition, a 5-month-old foal (Foal 10) of 174 admitted foals (>21 days and Equine Veterinary Journal ISSN 0425-1644 DOI: 10.1111/j.2042-3306.2011.00508.x 100 Equine Veterinary Journal 44, Suppl. 41 (2012) 100–104 © 2012 EVJ Ltd