TABLE 2: SEIZURES/HYPERSENSITIVITY
 

DISEASE	AETIOLOGY and EPIDEMIOLOGY	CLINICAL SIGNS	NECROPSY FINDINGS and DIAGNOSIS (D)
Cerebral babesiosis	Babesia bovis, transmitted by Boophilus microplus	Hyperaesthesia, nystagmus, circling, head pressing, aggression, seizures, and paralysis. Nervous signs may or may not accompany other signs of acute redwater	Cherry-pink colour of grey matter of cerebrum and cerebellum D: demonstration of parasites in brain smear
Heartwater	Cowdria ruminantium, transmitted by Amblyomma spp.	May die suddenly or, more commonly, show fever, hypersensitivity, ataxia, unsteady high-stepping gait or standing with head down making chewing movements. Later falling, lateral recumbency, paddling movements, seizures, opisthotonus, and death. Diarrhoea in some breeds	Necropsy may be negative, usually fluid in body cavities, oedema of lungs and abomasal folds and splenomegaly D: demonstration of organisms in brain smear
Nitrofuran poisoning	Acute toxicity in calves, occasionally in adult cattle; with recommended dosage or overdosing	Inappetence, hyperexcitability with incoordination, muscle twitching and convulsions. Syndrome usually resolves when immediately removed from medication	No gross lesions D: history
Urea poisoning	Ingestion of excess in licks or feed, or animals not accustomed	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
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
Organophos-phate 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	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)
Albizia poisoning	Pods of A. versicolor and A. tanganyicensis; late winter or early spring	Animals usually found dead. Survivors show hypersensitivity, staggering gait and tetanic seizures. Also wild expression in eyes, nystagmus and dyspnoea	Often cyanotic carcass; pods in rumen and seeds in reticulum D: history, pods/seeds in forestomachs
Annual ryegrass toxicosis	Ingestion of ryegrass seedheads containing nematode (Anguina sp.) galls infected by bacterium (Clavibacter sp.). Only reported from winter rainfall area of Cape Province	Usually not sudden death. Excitability, muscular twitching, unsteady, high-stepping gait. When handled or driven, epileptiform seizures with trembling, nystagmus and frothing at the mouth	Rapid rigor mortis, no gross lesions D: History, clin. findings, demonstration of bacteria or nematodes in affected seed heads
Hypomagnesaemia	Lactating dairy cows on lush, well-fertilized pastures. DD: ammonified hay toxicity	Usually acute onset of iritability, hyperactivity, tremors, falling, recumbency and eventually seizures. Subacute cases remain standing	No gross lesions D: clin. path.

TABLE 3: CHANGES OF BEHAVIOUR/ ALTERED STATE OF CONSCIOUSNESS
 

DISEASE	AETIOLOGY and EPIDEMIOLOGY	CLINICAL SIGNS	NECROPSY FINDINGS and DIAGNOSIS (D)
Hydrocephalus/ hydranencep-haly	Several causes including in utero viral infections e.g. BVDV; or hypovitaminosis A (uncommon)	Depression, lethargy, head pressing, convulsions or paresis/paralysis, dullness, blindness and weakness	Doming of skull and presence of hydrocephalus/hydranencephaly D: necropsy, serology, virus isolation
Malignant catarrhal fever ("snotsiekte")	Alcelaphine herpesvirus 1, occurring in 2 forms: wildebeest-derived and sheep-associated	Multisystemic disease: fever, nasal and ocular discharges, erosions of oral mucosa, panopthalmitis, lymphadenopathy etc., and encephalitis with tremors, ataxia, depression, wandering, aggression, and recumbency	No gross lesions of CNS D: history, clin. findings, pathology, virus isolation
Rabies	Lyssavirus serotype 1; transmitted by the bite of diseased mammals e.g. yellow mongoose, suricates, genets, wild felids, dogs	Early signs include separation from the herd, anorexia and docility or irritability. May develop paralysis of tongue and jaw with salivation, bellowing, aggression, and later, locomotory disturbances, tail paralysis, recumbency, paralysis, seizures, and death	No gross lesions D: immunofluorescence on brain (fixative 50% glycerosaline); histopathology lacks sensitivity
Sporadic bovine encephalomye-litis (SBE)	Chlamydia psittaci, in calves	Usually preceded or concurrent with generalized infection. May show fever, depression, and later stiffness, staggering, ataxia, circling and eventually falling with seizures and paralysis	± Serofibrinous meningitis and ventriculitis D: culture, demonstration of organisms, pathology
Trombotic meningioence-phalitis (TME)	Haemophilus somnus; most common in feedlot cattle 1-3 y old	Sudden death or fever, profound depression, reluctance to move, stiffness and knuckling of the fetlocks initially. Later may show tremors, blindness, circling, ataxia, paresis, paralysis, paddling, coma, and death	Multiple infarcts in grey and white matter of CNS D: culture, pathology
Bacterial meningitis/ meningioventri- culitis	In neonatal calves, often associated with another illness, e.g. enteritis, septisaemia; Pasteurella spp., coliforms and Corynebacterium spp.	Ataxia, paresis, hyperaesthesia, or depression, wandering, star-gazing, paddling in lateral recumbency, opisthotonus, nystagmus and seizures	± Congestion of meninges and lesions of concomitant disease D: culture, pathology
Cerebral theileriosis (turning sickness)	Theileria taurotragi, transmitted by Rhipicephalus appendiculatus; usually in young cattle less than 3 y	Sudden onset of nervous signs including circling, head pressing, blindness, ataxia, opisthotonos, and paralysis	Congestion and haemorrhages of meninges and brain, and malacic areas in brain D: demonstration of schizonts, pathology
Hepatic encephalopathy	Seen in chronic liver conditions e.g. chronic seneciosis	Head pressing, ataxia, seizures, blindness, coma and tenesmus	Cirrhosis of liver D: pathology
Lead poisoning	Often ingestion of pieces of batteries from farm dumps or old car oil. DD: Ornithogalum (chinkerinchee) toxicity	Ataxia, depression, seizures, hyperactivity, and twitching of the ears. May show salivation, wandering, blindness, head pressing, opisthotonos, bellowing and constipation	± Portions of batteries in rumen D: determine levels in blood, liver, kidney, and rumen contents
Dipcadi poisoning	D. glaucum	Animals walk drunkenly with flexion of fetlocks and knuckling over, and show circling, stumbling into trees, apathy, lying down with posterior paresis, and recumbency	No gross lesions D: history, clin. findings, plant identification
Stootsiekte ("pushing disease")	Matricaria nigellifolia	Docility, apathy, aimless wandering and pushing with the head against objects and incoordination with scuffing of the feet and knocking on	No gross lesions D: history, clin. findings, histopath.
Polioencephalo-malacia	= cerebro-cortical necrosis (CCN). Usually thiamine responsive, most common in feedlots. Also with high dietary sulphate and following water deprivation	Dullness, wandering, staggering gait, opisthotonos, tremors, blindness, head-pressing, and later recumbency with tonic-clonic convulsions, nystagmus, and opisthotonos	Brain oedema, ± laminar necrosis of cerebrocortical grey matter D: pathology, response to treatment
Ketosis (nervous acetonemia)	High-yielding cows in early lactation; single animals affected	Sudden onset; bizarre mental behaviour including chewing, licking of skin and objects, bellowing, hyperaesthesia. Also walking in circles, head pushing, apparent blindness	Fatty degeneration of liver D: history, clin. path
Hypocalcaemia (milk fever)	High-producing, mature dairy cows usually within 3 days after calving	Sudden onset of tetany or tremor with excitement and depression, paralysis, and unable to rise. Frequently they adopt a recumbent posture with head and neck turned toward the flank.	No gross lesions D: history, clin. path., response to treatment

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)
Listerial meningio- encephalitis	Associated with the feeding of silage	Depression, head tilt, circling, unilateral facial paralysis, dropped jaw, ataxia, recumbency, and panophthalmitis	No gross lesions D: culture, histopath.
Tetanus	Clostridium tetani, associated with deep penetrating wounds	Initially, increasing muscle stiffness followed by tetanic spasms of muscles, and hyperaesthesia. Also extended head, raised tail, slight abduction of legs, prolaps of 3rd eyelid, stiffness, constipation, dullness, and depression	No gross lesions D: history, clin. findings, culture, demonstration of toxin
Ionophore toxicity	Acute: 3-7 d after feeding of rations containing high levels of ionophores (formulation errors); chronic: 3 w or longer after feeding of poultry litter containing ionophores usually maduramicin	Sudden death or lethargy and recumbency, and signs of heart failure. Some may show stiff gait and tremors	Lesions of heart failure, ± mottling or pallor of myocardium in acute form; ± dilation of myocardium in chronic form D: feed analysis (confirmation difficult in chronic case), history, pathology
Dipcadi poisoning	D. glaucum	Walking drunkenly with flexion of fetlocks, ± circling, ± pushing against objects, posterior paresis	No gross lesions D: history, clin. findings, plant identification
Melia poisoning	Melia decumbens, in late winter and early spring following good winter rains	Initially swaying, unsteadiness and high-stepping gait. Later lying down and unable to rise, tremors	No gross lesions D: history, clin. findings
Kweek tremors	Ingestion of kweek grass (Cynodon dactylon) contaminated possibly by Claviceps spp.	Ataxia, tremors and walking with stiff hind legs, taking short steps, lifting legs high and frequently stumble and fall. Later, paresis progressing to paralysis and recumbency	No gross lesions D: history, clin. findings
Paspalum staggers	Cattle grazing on seedheads of P. dilatatum (Dallis grass) infected with ergots of Claviceps paspali	Hypersensitivity, tremors and incoordination, becoming more pronounced with exercise. May show recumbency and paddling	No gross lesions D: history, clin. findings
Maldronksiekte	Solanum kwebense, n & n-w Transvaal	Signs elicited when animals are disturbed, showing head tilt or rigid neck, star-gazing and ataxia or falling, seizures and collapse with tremors after regaining their feet	Atrophy of cerebellum D: history, pathology
White muscle disease	Selenium and/or vitamin E deficiency	May die suddenly after exercise; stiffness, trembling, weakness, inability to stand, recumbency	Pale streaks in tongue and neck muscles (congenital), skeletal muscles and myocardium (bil. simm.) D: feed analysis, histopath. of muscles

Compiled by JJ vd Lugt; the lists were reviewed by Drs PA Basson (Namibia), DJ Schneider (Stellenbosch), RD Last (Pietermaritzburg), and T. Shakespeare (Pretoria)

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