Introduction

Spiders of the genus Loxosceles are widely distributed across five continents¹, in Latin America, various species have been described. In countries bordering Bolivia, L. laeta is prevalent in Peru and Chile, while more distant species like L. reclusa are found in North America. Additionally, cases of envenomation caused by other species, such as L. gaucho in Argentina and L. intermedia in Brazil^2,3, have been documented. These spiders inhabit forested, temperate, tropical, rainy, chaparral, and desert regions¹.

Numerous components of Loxosceles venom have been identified, with studies focusing on the venoms of L. intermedia,L. reclusa,L. gaucho, and L. laeta⁴. The venom exhibits cytotoxic, necrotic, and proteolytic properties^5,6, primarily causing tissue destruction. Key components include Phospholipase-D, insecticidal peptides, alkaline phosphatase, cysteine and serine peptidases, metalloproteases, hyaluronidases, and sulfated nucleosides⁷.

Species within this genus are considered dangerous to humans due to the high morbidity and mortality associated with loxoscelism⁵. The venom’s effects can lead to medical complications, with clinical manifestations classified as cutaneous loxoscelism (the most common) and cutaneous-viscerocutaneous-hemolytic loxoscelism (less common). Symptoms range from pain and erythematous lesions to vasoconstrictive halos, ecchymotic plaques, vascular endothelial disorders, hemolysis, and severe necrotizing dermatological damage, which can be deforming, disabling, or even fatal depending on the severity of envenomation^6,8. Although cases of envenomation by Loxosceles spiders are suspected in Bolivia, they have not been described to date. Identification is crucial to providing primary care in emergency services or toxicology centers, as timely identification aids in clinical diagnosis and treatment effectiveness^2,5,7. Therefore, the objective of this study was to identify suspected Loxosceles specimens from the municipalities of San Benito and Tolata in the department of Cochabamba.

Materials and methods

Study Area. San Benito Municipality is located in the Punata Province of the Cochabamba Department, at an altitude of 2745 meters above sea level (17°30’54” S, 65°53’41” W)⁹. (Figure 1). It has an average annual temperature of 15.2° C, an average annual rainfall of 434 mm, and a relative humidity of 55 %, with the wettest months occurring between December and March¹⁰.

Tolata Municipality is located in the Germán Jordán Province of the Cochabamba Department, at an altitude of 2719 meters above sea level (17°31’47” S, 65°57’58” W)¹¹. (Figure 1). It has an average annual temperature of 26° C, an average annual rainfall of 401 mm, and a relative humidity of 66 %.

Specimen collection. Samples were provided by the Departmental Health Service (SEDES) of Cochabamba in July 2023 and preserved in 70 % alcohol. For genus confirmation, dichotomous keys by Gertsch & Ennik¹², Ríos¹³, and Grimaldo et al.¹⁴ were consulted. A stereo microscope (Ken-α-Vision, 20X magnification) was used for detailed observation and identification of arachnid characteristics.

Figure 1 Location of Tolata and San Benito in Cochabamba, the distance between both locations is 7748m 

Results

Examined material. 9 individuals were examined: 4 from San Benito (2 females: ILS-A 339, ILS-A 343, and 2 males: ILS-A 338, ILS-A 344) and 5 females from Tolata (ILS-A 340, ILS-A 341, ILS-A 342, ILS-A 345, ILS-A 346).

Figure 2 Corner spider in vivo 

Diagnosis. Spiders measured between 8-15 mm in length, with a dark brown or dusky brown cephalothorax and abdomen covered in abundant hairs (Figure 2). The violin-shaped cephalothorax had 3 pairs of eyes arranged in a triangular formation, with the first pair positioned anteriorly and the second and third pairs lateroposteriorly-a distinctive characteristic of the genus (Figure 3). The cephalothorax hairs were long and erect, covering one-third of the segment’s length.

Legs were brown, with the following length formula: 4, 2, 1, 3, ranging from 8-30 mm. Females exhibited a thin tubular epigynal lobe with an enlarged bulb at the apex, while males had long palpal segments and a curved embolus as long as the bulb’s width.

Discussion

The genus Loxosceles is known for its remarkable ability to colonize urban environments ^4,15,16. Specimens have been captured in attics, basements, wall crevices, under furniture, clothing, cracks, storage boxes, and gardens¹⁷. These spiders adapt effectively to new environments due to their generalist nature. However, specific factors facilitating species survival in these environments remain poorly understood¹⁷. Urban and peri-urban habitats provide abundant foraging opportunities and reduced presence of predators and competitors, aiding their spread¹⁸. In Bolivia, the colonization of Latrodectus in the city of Oruro provides a reference and alert for arachnid colonization patterns similar to those described by De Roodt et al.⁴ and Fukushima et al.¹⁶.

Figure 3 LEFT Loxosceles sp male, RIGHT Loxosceles sp. Female 

The spiders were captured at 2745 meters above sea level, a lower altitude than L. surca, described by Ríos¹³. However, species within this genus can inhabit altitudes up to 3774 meters above sea level, raising concerns for high-altitude regions in Bolivia¹³. Additionally, the description of L. surca in Chile is geographically close to the study area.

Currently, Bolivia lacks a specific antivenom for neutralizing Loxosceles venom. This is primarily due to limited and sporadic reports based on symptomatology and the absence of academic records of the genus in the country²⁰. Loxoscelism diagnoses are often delayed, primarily due to healthcare professionals’ lack of familiarity with the condition’s signs and symptoms, leading to patient referrals to other health centers²⁰. Moreover, diagnosing accidents caused by Loxosceles spiders can be challenging, as bites or spiders often go unnoticed, symptoms are not immediate, and some are nonspecific.

Loxosceles spiders have a lifespan ranging from 1155 days (males) to 1894 days (females). Females can produce up to 15 egg sacs during their lifetime, each containing 30-138 eggs. Juveniles reach adulthood after 9-12 molts, taking 315 days (females) to 406 days (males)³. Their considerable lifespan and biological adaptations make them highly dispersive, posing a significant public health concern due to their colonization of both urban and rural environments. Like other spiders, they can disperse aerially³.

Given the evident adaptability and dispersal capacity of the Loxosceles genus, combined with their long lifespan and reproductive rate, these factors favor the colonization of new habitats, enabling them to occupy a wide range of ecological niches^8,18. Therefore, it is recommended to conduct searches and collections of the genus Loxosceles across all departments in Bolivia to gather data on distribution, taxonomy, and epidemiological surveillance. This information could serve as a foundation for developing an anti-Loxosceles serum to mitigate risks to the population. This study confirms the presence of the genus Loxosceles in the communities of San Benito and Tolata in Cochabamba, Bolivia, highlighting the high valley as a potential risk area due to the presence of these spiders. The lack of arachnology specialists in the country limits the identification of Loxosceles species, leaving uncertainty regarding whether the species are native or shared with the region.