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This article was published in 1993
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Kikuyu (Pennisetum clandestinum) Poisoning
JG Boulton Regional Veterinary Laboratory, WOLLONGBAR
Kikuyu poisoning was first recognised in the north island of New Zealand in the 1960s, then in New South Wales and Western Australia in the early 1970s. It was particularly prevalent in NSW in autumn 1980, with 213 fatal cases amongst 1370 cattle on just 9 of the affected farms (Wong and others, 1987).
There have been sporadic incidents in NSW since 1980. Eight herds were affected on the north coast in 1991 (RVL Wollongbar records).
The toxin(s) which cause kikuyu poisoning is not known so the pathogenesis of the disease is not fully known.
History
Cases have typically occurred in late summer and autumn (February to June, incl.) and involved cattle grazing kikuyu pastures recently made lush by fertilisation, rain and/or irrigation after a long dry spell. Risk pastures have usually occupied a sheltered, humid microclimate. Stocking rate has typically been high.
There is no proof that pasture fungi are involved. New Zealand workers had incriminated Myrothecium roridum and M. verrucaria, which can elaborate toxic trichothecenes, but these fungi were absent from toxic pastures in Australia. Phoma spp., including P. herbarum var medicagensis, Fusarium semitectum, F. moniliforme var subglutinans and Penicillium spp. have been found in some toxic Australian pastures but not in all of them.
Nor is there proof that army worms are involved. Recent invasion of the pastures by army worms had been considered a factor in the Republic of South Africa (where 157 animals died of kikuyu poisoning on 7 farms in 1981) and in New Zealand but there was no such invasion in many of the Australian incidents (Gabbedy and others, 1974; Wong and others, 1987).
Clinical signs
* Depression, anorexia, reluctance to move
* Slobbering, sham-drinking and abdominal distension
* Dehydration and tachypnoea but no pyrexia
* Ataxia: high goose-stepping gait
* Sternal recumbency, then death
Lesions
* Forestomachs full of sloppy, green ingesta
* Pulmonary congestion and oedema
* Heart surface haemorrhages - an aetiologically non-specific agonal lesion
* Rumenitis, reticulitis and omasitis of which there may be gross evidence, but which should be confirmed histologically
* Renal tubular necrosis - detectable histologically or by clinical pathology
Clinical pathology
Consistent findings in 8 recent cases have been hyperkalaemia, hypochloraemia and azotaemia. As is usual in ataxic or recumbent cattle, CK is elevated.
Serum chemistry in 8 cows with kikuyu poisoning:
| Normal cows | Cows with kikuyu poisoning | |||
|---|---|---|---|---|
| Range | Range | No. abnormal | ||
| Sodium | mmol/L serum | 132-152 | 120-148 | 3 of 8 |
| Potassium | mmol/L serum | 3.9-5.8 | 4.8-8.7 | 6 of 8 |
| Chloride | mmol/L serum | 95-110 | 48-105 | 6 of 8 |
| Urea | mmol/L serum | 2.0-9.5 | 7.9-55.8 | 6 of 8 |
| Creatinine | umol/L serum | 90-240 | 204-770 | 6 of 8 |
| CK | U/L serum | 0-30 | 360-101,200 | 7 of 7 |
Recent cases of kikuyu poisoning
These are cases for which laboratory records of history, clinical signs, clinical pathology and lesions fit the descriptions given previously in this paper. Some records have no history; others have no description of signs. There was no serum from some cases, and no necropsy tissue from others.
| 1991 | ||
|---|---|---|
| May | Bootawa, Gloucester RLPD | History & lesions |
| June | Booral, Gloucester RLPD | History, signs, clinical pathology & lesions |
| June | Bunyah, Gloucester RLPD | History, signs & clinical pathology |
| Nobby's Ck, Tweed-Lismore RLPD | Signs & clinical pathology | |
| July | Nana Glen, Grafton RLPD | History & clinical pathology |
| October | Wollongbar, Tweed-Lismore RLPD | Signs, clinical pathology & lesions |
| November | Byangum, Tweed-Lismore RLPD | History & lesions |
| December | Gloucester, Gloucester RLPD | History, signs & lesions |
| 1992 | ||
| April | Aberdeen, Upper Hunter RLPD | History, signs & lesions |
Conclusion
There is no single definitive criterion by which to diagnose kikuyu poisoning. For a credible diagnosis these elements should be proved:
* History - recent grazing of lush kikuyu
* Signs - slobbering, sham-drinking, abdominal distension and dehydration
* Clinical pathology - azotaemia
* Lesions - rumen distended by sloppy green content, rumenitis and renal tubular necrosis
References
Gabbedy BJ, Gwynn R and others (1967) Kikuyu poisoning of cattle in Western Australia Aust. Vet. J. 50:369-370
Martinovich D, Mortimer PH and di Menna ME (1972) Similarities between so-called kikuyu poisoning of cattle and two experimental mycotoxicoses New Zealand Veterinary Journal 20:57-58
Newsholme SJ, Kellerman TS and other (1983) Intoxication of cattle on kikuyu grass following army worm (Spodoptera exempta) invasion Onderstepoort Journal of Veterinary Research 50:157-167
Wong PTW, Roth IJ and Jackson ARB (1987) Kikuyu poisoning of cattle in New South Wales and its relationship to pasture fungi in kikuyu grass Aust. Vet. J. 64:229-232