TABLE 2: SEIZURES/HYPERSENSITIVITY
 

DISEASE	AETIOLOGY and EPIDEMIOLOGY	CLINICAL SIGNS	NECROPSY FINDINGS and DIAGNOSIS (D)
Bacterial meningitis / meningio-ventriculitis	In neonatal lambs, often associated with another illness e.g. enteritis or septicaemia; Pasteurella spp., coliforms and Corynebacterium spp.	Ataxia, paresis, hyperaesthesia, or depression, wandering, star-gazing and seizures	± Fibrinous to purulent exudation of meninges; lesions of concomitant disease D: culture, pathology
Heartwater	Cowdria ruminantium, transmitted by Amblyomma spp. Very common	Initially show fever, hypersensitivity, an unsteady gait and listlessness, often standing with legs apart and head lowered and ears drooping. Later lateral recumbency, pedalling and chewing movements, opisthotonos, and death	Necropsy very seldom negative, usually fluid in body cavities, oedema of lungs and abomasal folds and splenomegaly D: demonstration of organisms in brain smear
Organophosphate and carbamate poisoning	Careless handling of pesticides resulting in contamination of feed or dips, or malicious poisoning	Overstimulation of parasympathetic system e.g. muscarinic: salivation, lacrimation, colic, diarrhoea, miosis; later nicotinic: muscle fasciculation and twitching, tremors, spasms, and hypertonicity causing stiff gait; CNS: anxiety, restlessness, and depression. Paralysis in chronic cases	No gross lesions D: demonstration of compound in suspected source and tissues (liver, fat, stomach content)
Chlorinated hydrocarbon poisoning	Careless handling of pesticides resulting in contamination of feed or dips, or malicious poisoning	Initially animal show apprehension, hypersensitivity or aggressiveness. Later fasciculation and twitching of muscles, and generalized intermittent or continuous spasms or seizures and death. May show ataxia and locomotor disturbances	No gross lesions D: demonstration of compound in suspected source and tissues (liver, fat, stomach content)
Prussic acid poisoning ("geilsiekte")	Ingestion of plants containing cyanogetic glycosides	Usually sudden death, but may show dyspnoea, cyanosis accompanied by anxiety, salivation, tremors, colic, convulsions, opisthotonos and rapid death	± Cherry red blood at necropsy D: necropsy, demonstration of cyanide in plants or in rumen contents, liver and muscle
Urea poisoning	Ingestion of excess in licks or feed, or animals not accustomed to intake; rain may cause leaching	Short clinical course. Initially show restlessness, hyperaesthesia or dullness, tremors and twitching of muscles. Also colic, ataxia, blindness, violent struggling and bellowing, and terminal tonic seizures elicitable by external stimuli	No gross lesions, or lung oedema and generalised congestion D: analysis of feed or licks, levels of ammonia in blood, serum, ruminal fluid, and urine, pH of rumen in fresh case
Cynanchum poisoning	Cynanchum spp. Mainly coastal s Cape Province. Rare	Initially wide-based stance, trembling, staggering and falling until recumbent. Then tetanic seizures, paddling movements often with opisthotonos and hypersensitivity. Survivors may show protracted paralysis	No gross lesions, ± plants in rumen D: History, clin. findings
Sarcostemma poisoning	S. viminale. Rare	Hypersensitivity, tremors and unsteady, stiff-legged uncoordinated gait. Later lying on side showing galloping movements, opisthotonos and extended legs. Survivors may show protracted paralysis.	No gross lesions D: History, clin. findings
Euphorbia poisoning	E. mauritanica; rare	Increased muscle tone and tremors. Reluctancy to stand, or standing with back arched and legs wide apart, diarrhoea	No gross lesions D: History, clin. findings
Annual ryegrass toxicosis	Ingestion of annual ryegrass seed heads containing nematode (Anguina sp.) galls infected by a bacterium (Clavibacter sp.). Only reported from winter rainfall area of Cape Province to date	Sudden death or excitability, muscular twitching, unsteady, high-stepping gait and convulsions with trembling, nystagmus and froth at the mouth	No gross lesions D: History, clin. findings, demonstration of bacteria or nematodes in affected seed heads
Phalaris staggers	Ingestion of Phalaris minor grass (canary grass); in Swartland of winter rainfall area. Rare	Sudden death (cardiac syndrome), or nervous form showing twitching and tremors, especially of the head. May carry on for weeks or months; worse when handled	Cardiac syndrome: lesions of heart failure; nervous form: ± greyish-green to bluish discolouration in brainstem, midbrain, spinal cord and dorsal root ganglia, and kidney D: history, pathology
Hypomagnesaemia	Ewes in late stages of pregnancy or early lactation grazing on lush pastures which have been heavily fertilised	Initially hypersensitivity with tetany, seizures and muscle twitching. Staggering gait, ataxia, rapid respiration, tremors, recumbency, clonic convulsions, coma and death. Disease usually follow short course	No gross lesions D: history, clin. pathology, response to treatment

TABLE 3: CHANGES OF BEHAVIOUR/ ALTERED STATE OF CONSCIOUSNESS
 

DISEASE	AETIOLOGY and EPIDEMIOLOGY	CLINICAL SIGNS	NECROPSY FINDINGS and DIAGNOSIS (D)
Rabies	Lyssavirus serotype 1; transmitted by the bite of diseased mammals e.g. yellow mongoose, suricates, genets, wild felids, dogs. Rare	Early signs include separation from the herd, anorexia and docility or irritability. May develop paralysis of tongue and jaw with salivation, sexual excitability, aggression (rare), and later, locomotory disturbances, tail paralysis, tenesmus, recumbency, paralysis, and death	No gross lesions D: immunofluorescence on brain (fixative 50% glycerosaline), immunocytochemistry; histopathology lacks sensitivity
Gedoelstiasis ("uitpeuloog")	Invasion and migration of first stage larvae of G. hässleri and G. cristata; occurs in sheep in direct or indirect contact with natural hosts e.g. wildebeest, hartebeest, blesbok, bontebok, tsessebe	Ophthalmic form: lachrymation, conjunctivitis, keratitis, protruding eye ball; encephalitic form: ataxia, staggering gait, circling, muscle spasms of head, hypersensitivity, opisthotonus, paresis, paralysis and death; cardiac form: sudden death	Malacia and haemorrhages in brain, lesions in blood vessels and eye, endocarditis D: history, clin. signs, pathology
Verminous encephalitis	Taenia multiceps cysts (Coenurus cerebralis)	Cysts in cerebrum (most common): gradual onset of depression, circling, head pressing, apparent blindness, inappetance. Cysts in vertebral canal: paresis, paralysis resembling ‘sitsiekte’	Cysts in brain or vertebral canal D: pathology
Strongyloides papillosus infestation (‘Gobabis boksiekte’)	In animals kept in kraals or small camps for prolonged periods; poor hygiene; poor rotational systems. Rare	Small number of animals may show ataxia, aimless wandering, circling, star-gazing, recumbency, and head-pressing. Also transient diarrhoea and cachexia	Cachexia, parasites in intestines, hepatosis, and occasional rupture of liver  D: worm egg count, path.
Dipcadi poisoning	Dipcadi glaucum	Aimless wandering, pushing against objects, diarrhoea, paralysis	No gross lesions D: history, clin. findings, plant identification
Oxalate poisoning	Associated with a number of plant spp., particularly vygies in n-w Cape Province and s Namibia, and Oxalis spp and Rumex spp in w Cape province	Acute: depression, weakness, coma, and death; subacute and chronic: depression, lethargy, stiff gait, recumbency and death	Nephrosis, and lesions of renal dysfunction and uraemia D: clin. path., pathology
Pregnancy toxaemia or ketosis ("domsiekte")	Very fat ewes in late pregnancy carrying twin lambs. Precipitated by any condition causing reduced feed intake, inadequate feed supply or rapid change in diet. Occasionally in thin ewes	Ewes became isolated from the flock, show inappetance, incoordination, champing of the jaws, frothing at the mouth, twitching of facial muscles, weakness and sternal recumbency. They are unaware of surroundings, apparent blindness, develop muscle tremors and convulsions, coma followed by death	Usually multiple pregnancy, empty rumen, fat necrosis and pale to yellow fatty liver D: history, clin. path., analysis of urine, pathology
Nitrate poisoning	Fertilisers, water, and variety of plant species: Amaranthus spp, Brassica spp, Sorghum spp, oats etc, especially after fertilisation	Hyperpnoea, dyspnoea, rapid, weak pulse, progressive cyanosis, methaemoglobinaemia (not always obvious), incoordination, anxiety, muscle tremors, convulsions and death. Abortion in surviving pregnant ewes	Methaemoglobinaemia - most prominent after carcase has been opened for an hour or more, pulmonary oedema and congestion D: diphenylamine test on plants, water or serum
Hepatic encephalo-Pathy	Seen in chronic liver conditions e.g. chronic seneciosis	Usually no overt signs. May show aimless wandering, depression, head pressing, apparent blindness, ataxia and recumbency, coma and seizures terminally	Chronic liver lesions D: pathology

TABLE 4: MOVEMENT DISORDERS (GAIT, POSTURE, ATAXIA OF HEAD AND LIMBS, AND VESTIBULAR DYSFUNCTION)
 

DISEASE	AETIOLOGY and EPIDEMIOLOGY	CLINICAL SIGNS	NECROPSY FINDINGS and DIAGNOSIS (D)
Listeria encephalitis	Listeria monocytogenes. Silage or spoiled feed. Rare	Progressive weakness, depression and paralysis to recumbency and death. May show ataxia, unilateral facial paralysis, dysphagia, head tilt, nystagmus and circling	No gross lesions D: culture, histopath. DD’s: otitis media/interna
Focal symmetrical encephalomalacia (FSE)	Chronic effect of Clostridium perfringens type D infection; sometimes with heavy worm infestation. Usually due to partial immunity. Common	Initial signs are ataxia, aimless wandering and blindness. May show dummy syndrome with head pressing. Lambs show recumbency, tremors, paddling and opisthotonos before death	± bilateral softening and haemorrhages in the midbrain D: history, pathology
Tetanus	Clostridium tetani, often after wounds from shearing, or tail docking and castration in lambs. Common	Initially, increasing muscle stiffness followed by tetanic muscle spasms, and hypersensitivity. Lambs have grinning facial expression, eyes wide, nostrils dilated, holding head high and legs wide apart, lateral recumbency, and stiffness of legs	No gross lesions; may see wound D: history, clin. findings, culture, demonstration of toxin
Brain abscess	Including peripituitary abscess ("bosluiskop"); sporadic; Corynebact. and Staph. spp. Common	Depend on localization of lesion. Depression, clumsiness, head-pressing, blindness are common signs. May see ataxia, circling, falling, recumbency with galloping movements, and nystagmus	Abscess in brain or peripituitary area, ± ticks around horns D: pathology (abscesses may be microscopic), bacteriology, smears
Polioencephalomalacia	= cerebro-cortical necrosis (CCN). Usually thiamine responsive, often in feedlots. Also with high dietary sulphate, following water deprivation, and certain ruminal disturbances. Common	Initially wander aimlessly, sometimes in circles, or stand motionless with blindness. Also head-pressing and star-gazing. Later recumbency with opisthotonos, extension of the limbs, hyperaesthesia, and tonic-clonic convulsions.	Brain oedema, ± softening and yellowish discolouration in the cerebral cortex grey matter D: pathology (lesions may show positive fluorescence), response to treatment
White muscle disease	Selenium and/or vit. E def. In young lambs < 2 months; may be congenital. Common	May die suddenly after exercise; stiffness, trembling, weakness, inability to stand, recumbency	Pale streaks in tongue and neck muscles (congenital), skeletal muscles (bil. simm.) and myocardium (right ventricle) D: feed analysis, histopath. of muscles

Compiled by Jaco van der Lugt; the lists were critically reviewed by Drs PA Basson (Grootfontein, Namibia), DJ Schneider (Stellenbosch) and RD Last (Pietermaritzburg) and Prof G Bath (Pretoria)

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