INTRODUCTION

Poisoning by Cestrum parqui (Solanaceae) occurs in several countries in South America (Riet-Correa et al., 2023). In Argentina, this poisoning occurs frequently in the central-north area of the country, with cattle being the most frequently affected species (Micheloud and Saravia-Peretti, 2014; Garcia et al., 2017; Costa et al., 2014). The toxicity of this species is due to carboxyatractyloside-type glycosides called parkin and carboxy parkin (Oelrichs et al., 1994). These toxins cause inhibition of mitochondrial respiration and ATP synthesis by altering the ADP / ATP carrier system through the membrane of the organelle, blocking the translocation of adenine dinucleotide in the cell (Lemasters, 1978).

When consumed, C. parqui, causes acute liver damage, characterized by the presence of generalized centrilobular necrosis (Matto et al., 2010; Riet-Correa, 1986; Costa et al., 2014), which rapidly leads to death (Riet-Correa, 1986; Costa et al., 2014). These plants affect several animal species, but cattle are the most frequently affected (Riet-Correa et al., 2023). Due to the severe and acute liver damage, the affected animals do not respond to any treatment, resulting in high lethality (Matto et al., 2010; Riet-Correa, 1986; Costa et al., 2014).

Several factors affect the probability of outbreaks due to the consumption of C. parqui in cattle— for example, variation in the concentration of toxic compounds in the plant and the presence of special conditions for it to be ingested (Matto et al., 2010). Management conditions where animals are restricted in feeding, such as lack of forage, prolonged drought, transport, or confinement, may lead to the occurrence of this intoxication (Riet-Correa, 1986; Costa et al., 2014).

This paper aims to describe a sequence of ten cases of Cestrum parqui poisoning in cattle in northwestern Argentina. The clinical, pathological, and epidemiological aspects of this occurrence are highlighted.

MATERIALS AND METHODS

A retrospective study on C. parqui registered cases was performed by the Animal health research area “Dr. Bernardo Carrillo” (IIACS, INTA Salta, Argentina). For the diagnosis of this intoxication, the presence of centrilobular necrosis along with the finding of the plant with evidence of having been consumed was considered (fig. 1B). The information from the corresponding reports was analyzed by compiling the clinical, pathological, and epidemiological aspects of the outbreaks.

Figure 1. A

Dead cattle found after being grazing in a field with abundant C. parqui plants. B- C. parqui mixed with Gatton panic forage. C- Bovine liver. Grossly marked diffuse lobular pattern in the surface and parenchyma (inset) were evidenced. D- Bovine liver. Microscopically, centrilobular multifocal necrosis could be observed (H&E. 4X).

RESULTS

In the period from 2015 to 2023, a total of 10 outbreaks of C. par considered one of the most common acutely toxic plants (Matto et al., 2010). In Argentina, this intoxication seems to be sporadic (Micheloud and Saravia-Peretti, 2014; Garcia et al., 2017); however, in northwestern Argentina, outbreaks occur frequently, as observed in this work.

All the clinical findings described in this work coincide with those mentioned in the literature (Riet-Correa et al., 1986; Matto et al., 2010; Micheloud and Saravia-Peretti, 2014). Clinical signs can be variable, and sometimes they may not be present, since several animals are found dead without showing any signs in some outbreaks as described herein. The most important pathological finding was hepatic centrilobular necrosis, which is similar to the findings described in intoxications caused by other species of the genus Cestrum (Riet-Correa et al., 1986; Furlan et al., 2008; Bandarra et al., 2009; Coutinho et al., 2013; Wouters et al., 2013; Oliveira et al, 2017) and other hepatotoxic species present in South America, such as Pascalia glauca and Xanthium strumarium (Machado et al., 2021; Medina et al., 2022).

Although Cestrum parqui is not the only plant capable of producing this type of lesion, the simultaneous findings of compatible clinical signs and the presence of the plant with evidence of having been consumed by the affected animals are enough to establish a strong presumptive diagnosis (Riet-Correa, 1986). It is worth mentioning that the micro-histological evaluation of ruminal content for the identification of Cestrum parqui can be an important diagnostic tool in cattle (Costa et al., 2014), but with little use at present due to the absence of specialists to carry out such studies. Moreover, the sensitivity and specificity of this diagnostic tool have only been tested in experimental conditions and not in natural cases, which may interfere with the interpretation of the results (Yagueddu et al., 1998). For this reason, ―in practice― the hallmark, of compatible clinical and pathological findings, associated with the presence of the plant with evidence of having been consumed and in the absence of other hepatotoxic agents, are considered sufficient to establish the diagnosis of this poisoning (Bailey, 2019, Medina et al., 2022).

As with other plants that produce hepatic necrosis, morbidity is variable, but lethality is high. In outbreaks of poisoning by C. parqui and other species of the same genus recorded in Brazil, morbidity ranged from 6.5 to 30%, and lethality was 100% (Riet-Correa et al., 1986; Furlan et al., 2008; Bandarra et al., 2009; Coutinho et al., 2013; Wouters et al., 2013; Oliveira et al., 2017). According to results from this study, the average incidence rate was 9.9±7.2% (Max=25% Min=2,7%) and lethality was 100% in all outbreaks.

In most outbreaks, deaths occurred between 3 and 10 days after the animals entered the infested lot. In only 3 of the total cases deaths were sporadic, with 1 to 2 animals per week over a period of up to 3 weeks. As described in the literature, deaths continued for 24 to 72 hours after the animals were removed from the infested lot (Riet-Correa et al., 1986; Furlan et al., 2008; Bandarra et al., 2009; Coutinho et al., 2013; Wouters et al., 2013). The present work showed that all categories can be affected—heifers and steers (50%), cows (30%) and calves (20%) respectively.

In northeastern Uruguay, this poisoning occurs throughout the year and problems due to this plant are accentuated during the drought years, when forage is scarce and there is a high stocking rate (Matto et al., 2010). In regards to the cases described in this study, although we cannot be conclusive, we can affirm that most outbreaks occurred during winter, a dry season in which forage supply is still low. However, in the state of Rio Grande do Sul, although outbreaks occur especially in spring, this poisoning does not seem to be related to lack of forage (Riet-Correa et al., 1986). In some of the cases described in this study, although there was not always a shortage of forage, the stocking rate was too high and the animals were forced to ingest other plants, such as C. parqui. Moreover, in many of the outbreaks described in this work, the plant was located near the trees surrounding the paddocks, next to the watering places. It is estimated that the animals remained in the shade of the trees when they went to drink water and to protect themselves from the sun, and that was the moment they ingested the plant.

Finally, plant poisoning is an ongoing problem for livestock throughout South America. However, despite its impact, the literature on this subject is scarce and is usually limited to the description of isolated cases. The epidemiological aspects described in this work contribute to the knowledge of C. parqui poisoning in northwestern Argentina and may be useful to mitigate the production losses caused by this plant.

Table 1.

Clinical and epidemiological data of the outbreak (date, affected category, location, incidence rate and context in which the poisoning occured.

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