Sawfly larval poisoning in cattle: Report on new outbreaks and brief review of the literature

Abstract

Sawϐly larval poisoning (SLP) is an acute hepatotoxicosis documented in livestock in Australia, Denmark and in countries of South America. It is caused by the ingestion of the larval stage of insects of the suborder Symphyta, order Hymenoptera, commonly known as "sawϐly". Three species of sawϐly are reportedly involved in the toxicosis. The insect involved in Australian SLP is Lophyrotoma interrupta (Pergidae), in Denmark the cause of SLP is the ingestion of the larvae Arge pullata (Argidae), and in South American countries documented outbreaks of SLP were caused by the ingestion of yet another sawϐly, Perreyia ϔlavipes (Pergidae). In all geographical areas where it occurred, SLP causes important livestock losses. In cattle, as well as in other affected species, the disease has a short clinical course and in many outbreaks affected cattle can be found dead. When observed, clinical signs include apathy, recumbence, tremors, paddling movements and death in 24-48 hours. Neurological signs such aggressiveness attributable to hepatic encephalopathy are also observed. In cases with a more protracted course icterus and photodermatitis may develop. Gross ϐindings included ascites, petechiae and ecchymosis over serosal surfaces of thoracic and abdominal cavities, and an enlarged liver that displays accentuation of the lobular pattern and edema of the gall bladder wall. Sawϐly larval body fragments and heads are consistently found in the fore stomachs and occasionally abomasum of affected cattle. Main microscopic lesions are restricted to the liver and consist of centrolobular (periacinar) to massive hepatocellular necrosis. In most lobules necrotic areas extended up to the portal triads where only a few viable hepatocytes remain. Mild to moderate lymphocyte necrosis is seen in lymphatic tissues. Cases occur in the winter months when the larval stages of the sawϐly are developing. D-amino acid-containing peptides have been found to be the toxic principle in each sawϐly involved in SLP. The octapeptide lophyrotomin is the major toxin in the in the larvae of Australian and Danish sawϐlies and is present in small amounts in the larvae of South American sawϐly. The heptadecapeptide pergidin is the main toxin in the South American sawϐly while small amounts of pergidin have been found in the other two species of toxic sawϐly. During the winter of 2011 (July-August) four outbreaks of SLP were diagnosed in the State of Rio Grande do Sul, Brazil. The ϐindings in those outbreaks are reported here and a brief review of the literature regarding SLP around the world is provided.

Natural and experimental poisoning by Cestrum laevigatum (Solanaceae) among cattle in the Agreste region of Paraíba, Brazil

“…However, all of these plants were neither native to Paraíba nor found in the paddocks where the outbreaks had occurred. Similar intoxications were also caused by Perreyia flavipes larvae (RAYMUNDO et al, 2009;TESSELE et al, 2012), but these were not observed in the pastures.…”

Poisoning of sheep by Vernonia plantaginoides (Less.) Hieron in Uruguay

“…Both diseases occur as a point epidemic with many animals found dead within a few days, while clinical signs of jaundice and photosensitization appear late in the outbreak, and the main autopsy finding is a "nutmeg liver" due to severe, diffuse, centrilobular hepatocellular necrosis. 10,26 Furthermore, the present outbreak was diagnosed in a county with a highly significant geographical clustering of sawfly poisoning in Uruguay (Dutra F, et al Descriptive statistics and spatiotemporal analysis of bovine hepatotoxic diseases diagnosed in Uruguay. Proceedings of the 8th International Symposium on Poisoning Plants, 2009 May 4-8, João Pessoa, Paraíba, Brazil), which can be explained by the fact that V. plantaginoides and P. flavipes larvae coexist on the same hilly grassland ecosystem of northeastern Uruguay and southern Brazil.…”

“…22,23 Although the present outbreak occurred in late summer to early autumn and sawfly poisoning occurs mostly in winter (June–September), 10 both diseases may overlap in time because cases of P. flavipes poisoning can occur in early autumn 10 and V. plantaginoides ( V. squarrosa ) poisoning is traditionally reported in August–November during shearing. 28 Thus, differential diagnosis between these diseases must rest on a careful postmortem examination, looking for chitinous fragments and larval heads with typical sensory hairs in the ruminal content 24 and, harder to notice, lymphocytolysis in the spleen and other lymphoid organs, which is widespread in sawfly poisoning 10,26 and minimal or absent in V. plantaginoides . Hepatogenous photosensitization in sheep grazing plants containing lithogenic saponins produces rather similar clinical signs (“yellow big head”) both in eastern Uruguay ( Heliotropium ocellatum , unpublished data) and southern Brazil ( Brachiaria spp.…”

Toxic Peptides Occur Frequently in Pergid and Argid Sawfly Larvae

“…Since the mid-20 th century there have been uncommon but repeated reports of livestock dying after ingesting certain insects. Hundreds of cattle, sheep, goats, and pigs have been found dead, with significant economic consequences to the farmers [10] – [12] , first in eastern Australia [13] , [14] , then in Denmark [15] , and South America [12] , [16] , [17] . The mammals perished after grazing in areas showing congregations or outright outbreaks of larvae belonging to one of two sawfly families, Pergidae or Argidae.…”