oat crop grazing were moist and slightly warmer than usual with monthly rainfall and maximum and minimum temperatures as follows: April, 83 mm, 26.6”C, 83°C; May, 29 mm, 15.7”C, 4.7”C; June 10 mm, 14.2”C, 3.1%. Fly strike activity continued into the winter months, the last recorded strike occurring on 19 June 1972. The incidence of breech strike between 26 April and 21 June is shown in Table 1. During the periods of oat crop grazing there was a high incidence of breech strike in both mulesed and unmulesed sheep, although more of the unmulesed weaners were struck ( 5 2 % for mulesed, uncrutched, versus 87% for unmulesed). Among the mulesed sheep those carrying 1 1 to 12 months’ wool appeared to be more susceptible ( 5 2 % ) than those carrying 6 to 7 months’ wool ( 3 3 % ) , but this difference was not statistically significant. Breech strike is a collective term, comprising crutch strike and tail strike. Crutch strike involves the region below the tail base, extending on both sides of the perineal “bare area” down t o the distal border of the udder or scrotum. Tail strike involves the body of the tail, frequently originating on the stump or sides of the tail. Crutch strike was the main type in unmulesed weaners before oat grazing and was associated with urine staining, whereas tail strike predominated in both

mulesed and unmulesed sheep after grazing on oats had led to scouring (Table 1 ) . The tail wool in short-tailed shsep tends to drop downwards over the anus where it is readily wetted by diarrhoea, which may account for the greater incidence of tail strike than crutch strike. Nevertheless, it can be concluded that, without a recent crutching, the Mules operation in short-tailed sheep did not provide substantial protection against breech strike associated with scouring. J. E. WATTS, B.V.Sc. CSIRO Division of Animal Health. McMaster Laboratory, Glebe. South - Wales. 2037 , New D. A. PERRY, H.D.A. New South Wales Department of Agriculture, Agricultural Research- Station, Temora, New South Wales, 2666 30 June I975 References Belchner, H. G. ( 1 9 3 7 ) S c i . Bull. Dep. Agric. N.S.W. No. 54. Dun, R. B. (1954)-Aaric. Gaz. N.S.W. 65: 124. Graham, N. P. H., Johnstone, I. L. and Riches, I. H. (1974)-Ausf. vet. J . 23: 3 1 . Joint Blowfly Committee (1933)-Purnph. Coun. scienf. ind. Res. Ausf. No. 37. -

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TOXICITY TO LIVE6TOCK OF THE BLUEaREEN ALGA ANABAENA CIRCINALIS The occurrence of the waterbloom, Anabaena circinMouse toxicity tests as described by McBarron and aCis in New South Wales and its toxicity by mouse tests May (1966) indicated a highly potent toxin in the has been reported by May (1972) at Braidwood and sample. May and McBarron (1973) reported similarly from Infested water was administered orally to White LegBurrinjuck Dam together with poisoning of honey bees horn chickens, 5 weeks of age, with an average weight by this waterbloom from Finley. No reference has been of 250 g, either with a syringe and polythene tubing or found t o poisoning of livestock by A . circinrrlis although ad lib from drinking vessels. Standard laying mash Schwimmer and Schwimmer (1964) record animal was available ad fib and drinking water available except intoxications by unidentified species of Anabaena. The for the group restricted to the infested water. Treattoxicity of A. f7m-aquae has been investigated by Car- ments extended over 5 days. Fifteen days after commichael et al (1975). mencement all surviving birds were slaughtered and The initial observation concerned the death of 20 of autopsied. 500 Corriedale lambs, 10-months-old, who obtained Group I : Five birds received 5 ml infested water orally water from a dam (ground tank) on a farm of 1288 by syringe daily. hcctares at Young, in southern New South Wales in late Group 2: Five birds allowed infested water only withMay 1975. The dam of 700 ms capacity, provided out restriction. water to 4 paddocks, each isolated by north-south, east-west fences intersecting at the dam centre. The Group 3: Of 6 birds, 2 were dosed with 10 ml of infested water and 4 with 5 ml daily. dead lambs were found in the SE paddock after 48 Throughout the tests all birds remained clinically hours access to the water during which time a north west wind concentrated a bloom of Anabaena circinalis normal with no deaths. After 2 days of the trial, one bird from group 2 and in the south east quadrant of the dam. Clinical signs noted were trembling, salivation, staggering, leg weak- also group 3 (low dose) showed no lesions on autopsy. In birds autopsied on the 15th day, there were no ness and collapse. N o autopsies were performed but some of the lambs had a green scum of algae on their lesions in group 1 ; 3 of the 4 birds in group 2 showed legs. Of the 20 dead, 2 died within 9 0 m of the dam a pale tan liver with focal haemorrhagic plaques u p to 1 cm in diameter. The remaining bird had diffuse redand 18 within a radius of 550-600 m. At the same time 800 Corriedale ewes and rams and 40 head of Short- dening of the liver. The kidney of the one bird examhorn cattle watering from the south west quadrant of ined displayed tubular degeneration and the accumulation of eosinophilic casts within the tubules. The liver the dam were unaffected. A sample of infested water at this time contained exhibited vacuolation and swelling of the hepatic cytomuch A d a e n a circinalis and some Schizothrix calci- plasm, loss of tubular arrangements and narrowing of cola. The latter is also a member of the Cyanophyta sinusoids. and is often associated as a subdominant species with In group 3 the liver changes were more pronounced waterblooms (May 1972). It can form a waterbloom macroscopically with focal, subcapsular haemorrhagic itself and has been collected in many habitats of marine plaques of circular to elliptical shape, varying from and fresh waters from all regions of the world (Drouet 0.5 to 2 cm in diameter. There was a loss of normal parenchymatous arrangement with swelling and vacuola1968). It can produce a toxin in a marine environment. This toxin is suspected of being transmitted through fish tion of the hepatocytic cytoplasm with fragmentation of chromatin within some hepatocytic nuclei. The overall to man (Banner 1966). Australian Veterinary Journal, Vol. 51, December, 1975

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picture was an acute degenerative change. The kidneys showed severe tubular degeneration. A further sample of the waterbloom from the same dam, was collected 7 days later. Although a potent toxin was demonstrated in mice, the oral administration of 6.1 f of water over 4 days to a wether, failed to produce evidence of malaise nor any gross or histopathological lesions. The rapid changes in toxicity of algaeinfested water has been noted by May and McBarron (1973). Acknowledgment is given to Valerie May of the National Herbarium, Royal Botanic Gardens, Sydney for the identification of the algae and information on ScNzothrix ralricola. ..... ..... . *E. J. McBARRON, B.V.Sc. tR. I. WALKER, B.V.Sc. *I. GARDNER. B.V.Sc. *K.H. WALKER, B . v . ~ . I5 August 1975 *Veterinary Research Station Glenfield New South Wales 2167. ?Pastures Protection Board. qoung. Nek South Wales 2594.

References Banner, A. H. (1966)-“Marine toxins from the Pacific. I. Advances in the investigation of fish toxins”, in “Animal Toxins”, Ed. S. E. Russel and T. R. Saunders, Pergamon Press, New York. Carmichael, W. W., Biggs, D. F. and Gorham, P. R. (1975)Sc ie nc e 187: 542. Drouet, Francis ( 1968)-Revision of the classification of the Oscillatoriaceae. Monograph No. 15, The Academy of Natural Sciences of Philadelphia, Fulton Press Incorporated, Pennsylvania. McBarron, E. J. and May, Valerie (1966)-Aust. vet. 1. 42: 449. May, Valerie (1972)-BuN. Dept Agriculture, N.S.W. Sci. Bull. 82. May, Valerie and McBarron, E. J. (1973)--5. Ausi. Inst. Agric. Sci. 39: 264. Schwimmer, D. and Schwimmer, M. (1964)-“Algae and Medicine”-‘“Algae and Man”, Ed. D. F. Jackson, Plenum Press, New York.

HORNER’S SYNDROME Jones and Studdert (1975) described 4 c a m of vertebrate eye (oculus) and the muscles which provide Homer’s Syndrome (HS) in 2 dogs and 2 cats. The for its movement are contained within the orbit. The diagnostic conclusions of the authors. based upon the extraocular muscles (muscular bulbi), conjunctiva, signs evidenced in 2 of these animals, are suspect. In palpebral ligaments and periorbital fat suspend and addition, the introductory portion of their article con- cushion the eye (Miller et nl 1964). All these struo tains inaccuracies of normal anatomy and physiology. tures surrounding the eye form a scaffolding that keeps The iris has not 1, but 2 smooth muscles that govern the eyeball in position. The forward and backwards pupillary size. They are the sphincter pupillae supplied displacements of the eye in man are much more limited than those possible for the lower animals; the latter by the parasympathetic fibres of the oculomotor nerve, possessing a sheet of muscle between the insertions of and the dilator pupillae innervated by the sympathetic efferents of the cervical sympathetic chain that arise in the recti, arising a t the apex of the orbit. This is known the first 2 thoracic segments of the spinal cord, with as the retractor bulbi muscle (Moses 1970). The reoccasional contributions from the eighth cervical and tractor bulbi is a striated muscle and is innervated by the motor abducens nerve and not by the sympathetics. third thoracic segments (Moses 1970). HS in. animals is characterised by a tetrad of usual The elevation of the upper eyelid is the function of the levator palpebrae superioris, a striated muscle con- signs: miosis, slight ptosis, enophthalmos and the protrusion of the third eyelid. I n arriving at any diagnostic trolled by the motor portion of the oculomotor nerve. The lower eyelid has n o levator muscle as such, but it conclusions based upon clinical signs, it is important can be elevated by the action of the sphncter-like to understand the physiology of the signs and t o realise that some signs are shared with yet other disease proorbicularis oculi muscle, another striated muscle that is innervated by the auriculo-palpebral branch of the cesses. The miosis seen in HS is due to the interruption of facial nerve. The action of this muscle is t o narrow the dilator pupillae’s innervation permitting the or close the palpebral fissure as occurs in the act of blinking and in cases of blepharospasm due to ocular sphincter pupillae’s tone to predominate. Miosis may pain. The palpebral fissure size is governed by the also be seen in cases of uveitis for another reason, the action of the latter 2 mentioned muscles in addition to irritative effect of the inflammation upon the ins the action of the superior tarsal muscle (synonyms = sphincter, which is the stronger of the 2 antagonistic Mueller’s muscle, superior palpebral muscle). The muscles, resulting in a constricted pupil. The position of the third eyelid is dependent upon superior tarsal muscle IS nonstriated and lies just beneath the conjunctiva. It is attached at its [email protected] the the relationship of the eyeball to the bony orbit and inner aspect of the levator palpebrae supenons and the other orbital contents, as well as to a neuromuscular control. In HS the third eyelid is protruded inserts into the upper portion-of the tarsal plate (%he$ and Albert 1969). The tonic state of this muscle is across the eye because of the loss of tone in a sympathetically controlled smooth muscle at the base of the instrumental in maintaining the normal size of the palpebral fissure, but it cannot of its own accord elevate third eyelid. This muscle holds the thud eyelid in a the upper eyelid, except perhaps in the case of extreme retracted position. Protrusion may occur for a number fright. It is the loss of tone in this muscle, which has of other reasons. In the cat, a mechanism exists for active protrusion via striated muscle fibres from the a sympathetic innervation, that results in the ptotic lid in HS. However, since the levator palpebrae superioris lateral rectus muscle to the third eyelid. These muscle functions normally in an uncomplicated case of HS the fibres are innervated by the abducens nerve (de resulting lid droop is only slight. In cases of paralysis Lahunta 1973). Blogg (1975) stated that retrobulbar of the levator a severe ptosis is seen,even if the superior space occupying lesions, as well as ocular pain, can cause the third eyelid to become prominent. In the tarsal muscle’s action is normal. case of ocular p a n it is the spasm of the retractor There are n o muscles, striated or nonstriated, that maintain the forward position of the eyeball. The bulbi muscle which causes an enophthalmos of sufficient 588

Australian Veterinary Journal, Vol. 51, December, 1975