CLINICAL SIGNS
Neural angiostrongyliasis should be considered in the differential diagnosis for any species of wildlife presenting with neurological signs. Migrating late third- or fourth-stage larvae or young adults cause multifocal neurological disease.
Clinical signs are variable, reflecting host inflammatory response, random migration and location of parasites within the CNS and variable numbers of worms. The disease may be acute or chronic (up to several weeks) and clinical signs may be subtle or severe or wax and wane. Paresis or paralysis, particularly affecting the hindlimbs is a common presentation in Australian mammals, allowing a presumptive antemortem diagnosis to be made if spinal trauma and tick paralysis can be ruled out (Ma et al. 2013). In flying-foxes, an important differential diagnosis is Australian bat lyssavirus infection (ABLV) (see Chapter 34). Flying-foxes with NA may resemble those with the ‘paretic’ form of ABLV infection; however, most bats with ABLV rapidly deteriorate within 24-48 hr, whereas most with NA have a comparatively prolonged (>3 d) and stable clinical course. Some flying-foxes with NA also have periods of temporary improvement, which is not seen with ABLV (Barrett 2004). In most species, NA can affect any age group; however, there may be a higherincidence in young animals, which was seen in one study of hand-reared juvenile common brush-tailed possums (Ma et al. 2013). This is more likely the result of behavioural indiscretion or naivety in consumption of intermediate or paratenic hosts rather than greater susceptibility. Outbreaks where several animals in a group are affected have been reported. Clinical signs have been documented in various Australian mammal species (Gordon 1992; Higgins et al. 1997; McKenzie et al. 1978; Reddacliff et al. 1999; Barrett et al. 2002; Barrett 2004; Vogelnest and Woods 2008; Ladds 2009; Ma et al.
2013; Vogelnest, unpublished) and include:• unilateral or bilateral hindlimb paresis or paralysis, unilateral or bilateral forelimb paresis or paralysis, tetraparesis, tail paresis, ataxia, proprioceptive deficits, forelimb spasticity, recumbency, hindlimb muscle atrophy
• nystagmus, anisocoria, mydriasis, loss of pupillary light reflex, head tilt, circling (common in platypuses, Ornithorhynchus anatinus [Australia Zoo Wildlife Hospital records]), tremors, unilateral or abnormal facial and cervical muscle contractions, opisthotonic spasms, reduced mentation, profound central depression, seizures, coma, death
• lethargy, frothing at the mouth, shivering, weakness, debility, anorexia, poor body condition
• inability to fly or hang, respiratory distress, abortion (bats)
• urine retention, incontinence
• tachyarrhythmia, tachypnoea, dyspnoea
• excessive grooming.
Fig. 24.2. Angiostrongylus cantonensis nematodes (arrows) beneath the meninges of the cerebellum and cerebrum of a common wallaroo (Osphranterrobustus). Photo: Roger Kelly
Fig. 24.3. Photomicrograph of the brain of a parma wallaby (Notamacropusparma) showing four transverse sections of Angiostrongylus nematodes within meningeal blood vessels. There is minimal associated inflammatory response. Haematoxylin and eosin (ARWH 2018 case no. 6858.1).
4.