Acute and chronic nervous signs in cattle associated with Phalaris angusta poisoning in Argentina

Abstract

Phalaris angusta is a South American natural grass that produces poisoning in sheep and cattle in Argentina and Brazil. Phalaris spp. can produce unrelated forms of poisoning in ruminants, acute and chronic syndromes. The objective of this paper was to describe an outbreak of acute and chronic Phalaris nervous syndrome in 53 of 980 fattening steers and heifers in a farm of Buenos Aires province. On September of 2006 the animals developed nervous signs and died after 3-5 days. The herd was removed to a phalarisfree pasture. Three months later (on December) 15 new clinical cases developed in the herd. Necropsy performed in one affected calf showed neither grossly nor microscopic changes. Microscopically, there were no major alterations in tissues. Nervous signs had been described in some field cases where neither pigment deposition nor axonal degeneration could be detected. Clinical findings displayed by affected cattle after consumption of Phalaris angusta pastures resemble those observed by other authors in Phalaris staggers. This is the first report in Argentina where both syndromes were seen in the same herd.

Retrospective analysis of cattle poisoning in Argentina (2000-2013)

“…Phalaris. angusta is a natural grass widely distributed in our region and the main species identified in the Argentine outbreaks (Cantón et al 2010). As previously mentioned, Paspalum spp.…”

Plants causing poisoning outbreaks of livestock in South America: A review

“…Their toxicity is higher when the plants are young and growing. Phalaris angusta is a South American natural grass that produces poisoning in sheep and cattle in Argentina ( Cantón et al, 2010 ; Odriozola, 2011 ), Uruguay ( Riet-Correa et al, 1993 ), and Brazil ( Gava et al, 1999 ).…”

“…The sudden death syndrome does not occur in South America, and its pathogenesis is unclear. Only Phalaris staggers are reported in South America ( Riet-Correa et al, 1993 ; Gava et al, 1999 ; Cantón et al, 2010 ; Odriozola, 2011 ).…”

Phalaris Toxicoses in Australian Livestock Production Systems: Prevalence, Aetiology and Toxicology

“…McDonald first described toxicity in grazing livestock resulting from ingestion of phalaris in 1942 [21]. Subsequently, outbreaks were reported in New Zealand [22], America [8], and Argentina [23] with most reported in livestock grazing P. aquatica. However, toxicity has also been documented in stock grazing P. angusta [7], P. arundinacea [8], and P. caroliniana [9].…”

“…In cattle, clinical signs of phalaris 'staggers' are not well reported as the incidence is relatively rare compared to that in sheep [26]; however, neurological changes also include ill-coordination, muscle tremors, excessive salivation, lethargy, failure to thrive, a reduced ability to swallow and falling [8,21,23]. There have been some attempts to administer pharmacological agents to control this syndrome and both 'Myanesin' and barbiturates have been shown to be an effective treatment for acute phalaris 'staggers' in livestock [30].…”