Primary photosensitization caused by Chamaecristas serpens var. serpens in horses, donkeys, cattle, and goats.

Overview

• This research reports an outbreak of primary photosensitization in multiple livestock species caused by the plant Chamaecrista serpens var. serpens in Bahia, Brazil.
• The study details the clinical signs, prevalence, and recovery of affected horses, donkeys, cattle, and goats, emphasizing the plant’s economic impact on regional livestock farming.

Introduction and Background

• Chamaecrista serpens var. serpens is a plant species that grows in the semi-arid region of Bahia, Brazil.
• Primary photosensitization occurs when photosensitive compounds in plants cause skin reactions in animals upon exposure to sunlight, especially in areas with less pigmentation or hair.
• Different livestock species such as horses, donkeys, cattle, and goats are susceptible to photosensitization caused by certain plants.
• This study focuses on an outbreak involving Mangalarga Marchador horses, Pega donkeys, Nelore cattle, and Mambrina goats.

Outbreak Description and Conditions

• The outbreak was detected in the municipality of Iaçu during the initial 15-30 days of the rainy season, coinciding with the regrowth phase of C. serpens var. serpens.
• The regrowth and high abundance of the plant increased exposure and intake by the animals.
• The plants were highly palatable for animals, promoting ingestion and subsequent poisoning.

Prevalence Among Species

• Prevalence rates differed among species:
• Donkeys and horses had the highest prevalence, with 100% of animals affected.
• Cattle had a significantly lower prevalence, with only 11.9% affected.
• Goats showed an intermediate prevalence at 38.8%.
• The high prevalence in donkeys and horses indicates these species might be particularly susceptible or have more access to the plant.

Clinical Signs Observed

• The clinical presentation was typical of photosensitization:
• Intense itching (pruritus)
• Edema or swelling in affected areas
• Crust formation on the skin
• The lesions predominantly occurred in areas of non-pigmented skin or with less hair coverage, such as light-colored or sparsely haired regions.
• Animals sought shade, a behavioral adaptation to reduce pain and photoactivation of the toxins, noted especially in horses.
• Two horses died, indicating that the severity of skin lesions and possibly secondary complications can be fatal.

Impact and Recovery

• The plant’s high availability and palatability lead to widespread clinical cases, causing significant economic loss in the livestock industry.
• Affected animals were removed from the contaminated areas to regions where C. serpens was absent and shaded environments were available, leading to recovery within 21-28 days.
• The study highlights the importance of managing invasive plants to prevent repeated outbreaks and protect animal health.

Conclusions and Recommendations

• The research confirms that C. serpens var. serpens can induce primary photosensitization in multiple livestock species.
• Such poisoning has direct economic implications by causing morbidity, mortality, and production losses.
• There is a need to develop and implement control strategies to manage the spread and abundance of this invasive plant.
• Management strategies could include:
• Monitoring and eradicating C. serpens in pastures
• Providing alternative forage and shaded areas during high-risk periods
• Educating farmers and veterinarians about risks and early signs of photosensitization