Nathaniel C. Elston, BA

Triatome bugs cause painful bites and serve as vectors for Chagas disease. In this article, we will address diagnosis and vector identification.

Key Morphologic Features

Insects from the subfamily Triatominae are identifiable by their long legs and a shieldlike abdomen behind a platelike pronotum that covers the thorax. Their half-membranous wings overlap, covering the central abdomen but leaving the lateral portions visible. Tigerlike stripes are characteristically prominent on the visible portions of the lateral abdomen. The stalklike head has an articulated beaklike mouth that can be retracted and used to deliver a powerful bite (Figure 1).

Feeding Mechanisms and Host Reactions

Triatome bugs are blood-feeding arthropods that hide in cracks and crevices in domestic structures by day and feed at night. They are shy feeders, and laboratory colonies have been known to die rather than feed in daylight. They are particularly common in thatched or wattle-and-daub dwellings, where they can be present in great numbers and descend on sleeping inhabitants at night. Triatome bugs require regular blood meals throughout the 5 developmental nymph stages in order to undergo successful molting.

In the wild, triatome bugs feed on a range of animals with little specificity, but in domestic settings they feed largely on humans. Thermosensors in the antennae help them locate blood vessels under the skin, which they penetrate easily due to their long mouthparts. Like other blood-sucking arthropods, they release an anticoagulant that facilitates continuous blood flow while feeding, which accounts for many of the cutaneous reactions observed after the host sustains a triatomine bite.¹

Triatomine bugs have trouble feeding through clothing and seek out exposed skin, particularly the eyelids, producing the characteristic unilateral eyelid swelling known as the Romaña sign. Other bite reactions include purpura; macular erythema; and vesiculobullous, papular, and urticarial lesions (Figure 2).² Associated lymphangitis or lymphadenopathy may be noted, and anaphylaxis has been reported. Similar to those of cockroaches, triatome antigens have been associated with atopic dermatitis and asthma.³

Chagas Disease Risk and Transmission

Triatomine reduviids are the primary vector of Chagas disease, and the geographic range of both continues to expand, particularly in North America. The disease remains endemic in Latin America, with the highest incidence now reported in Brazil.⁴ An estimated 240,000 to 350,000 individuals in the United States are infected, primarily immigrants from Mexico, Central America, and South America; approximately 30% of those infected will develop cardiac and/or gastrointestinal complications.⁴ If left untreated, Chagas disease leads to autonomic ganglion destruction and subsequent gastrointestinal and cardiac complications, including megacolon, dilated cardiomyopathy, and heart failure.⁵

Trypanosoma cruzi, the microorganism responsible for Chagas disease, is spread to humans through triatomine fecal matter scratched into the bite wound.⁶ Triatomine bugs have a highly developed gastrocolic reflex and defecate liberally as they feed. Fecal volume is heavily dependent on species and sex, with fifth-stage female nymphs producing the highest volume of excrement and thereby acting as particularly adept disease vectors.⁶ Triatoma infestans and members of the genus Mepraia are key vectors of T cruzi.¹ In areas of South America where populations of T infestans are controlled through public health measures, Mepraia emerge as a largely uncontrolled disease vector.^1,7 While endemic to the southern United States and South America, T cruzi has spread to much of North America and Europe by way of Triatominae as naturalized or invasive species.⁸

There are 3 phases of Chagas disease: acute, indeterminate, and chronic. A chagoma is a localized erythematous swelling at the site of the bite. The acute phase often lacks systemic symptoms but may include fever, myalgia, and headache. The intermediate phase may include fatigue and recurrent fevers. The most serious manifestations occur in the chronic phase and include cardiomyopathy with signs of congestive heart failure, irregular heartbeat, cardiac arrest, abdominal pain, constipation, and dysphagia.

Deforestation has been identified as a driving factor in the spread of Chagas disease, as the disease vectors shift from wilderness areas and animal hosts to inhabited areas where humans are the most readily available food source. Triatome bugs in areas experiencing higher levels of development or forest harvesting are forced into human-populated areas. As a result, instances of Chagas disease are on the rise in these communities.⁷ Salvador, Bahia, Brazil, has been identified as one such target of increased vector presence due to heavy deforestation, and the hottest months were identified as having the greatest threat of vector exposure.⁹ Brazil became the leading geographic area for the disease partly because of heavy loss of forested land.¹⁰

Vector Control and Prevention Strategies

Elimination of cracks and crevices in walls; replacement of wattle and daub with stucco, plaster, and other solid building materials; and the use of insecticides with durability in the environment have been used to reduce triatome bug infestation in homes. However, highly persistent insecticides carry greater environmental risk and may drive resistance as declining concentrations select for resistant arthropods. Repellents have less environmental impact and play an important role in vector control. Citronella essential oil has been observed to repel several species of triatome bugs that are common in Arizona; specifically, the component alcohols geraniol and citronellol were found to be effective at inhibiting triatome feeding.¹¹

Early detection of Chagas disease is essential, as end-stage cardiomyopathy and megacolon are difficult to treat. Newly developed multiantigen testing has shown promising results, suggesting a potential for more accurate testing for Chagas disease.⁸ Geospatial tracking and mapping of T cruzi vectors now are employed to track seasonal vector changes and disease patterns.⁹ Researchers also have developed a dedicated dichotomous key for the identification of triatome bugs endemic in Brazil with the hope of better identification and mapping of disease vector presence and density.¹⁰ The key consists of a series of statements with 2 choices in each step. It uses observable features of the arthropod to lead users to the correct identification.

Final Thoughts

Identification of triatome bugs can help with public health efforts to control the spread of disease. Patients with unilateral eyelid swelling should be evaluated for possible bedbug or triatome exposure.

Triatome bugs cause painful bites and serve as vectors for Chagas disease. In this article, we will address diagnosis and vector identification.

Key Morphologic Features

Insects from the subfamily Triatominae are identifiable by their long legs and a shieldlike abdomen behind a platelike pronotum that covers the thorax. Their half-membranous wings overlap, covering the central abdomen but leaving the lateral portions visible. Tigerlike stripes are characteristically prominent on the visible portions of the lateral abdomen. The stalklike head has an articulated beaklike mouth that can be retracted and used to deliver a powerful bite (Figure 1).

Feeding Mechanisms and Host Reactions

Triatome bugs are blood-feeding arthropods that hide in cracks and crevices in domestic structures by day and feed at night. They are shy feeders, and laboratory colonies have been known to die rather than feed in daylight. They are particularly common in thatched or wattle-and-daub dwellings, where they can be present in great numbers and descend on sleeping inhabitants at night. Triatome bugs require regular blood meals throughout the 5 developmental nymph stages in order to undergo successful molting.

In the wild, triatome bugs feed on a range of animals with little specificity, but in domestic settings they feed largely on humans. Thermosensors in the antennae help them locate blood vessels under the skin, which they penetrate easily due to their long mouthparts. Like other blood-sucking arthropods, they release an anticoagulant that facilitates continuous blood flow while feeding, which accounts for many of the cutaneous reactions observed after the host sustains a triatomine bite.¹

Triatomine bugs have trouble feeding through clothing and seek out exposed skin, particularly the eyelids, producing the characteristic unilateral eyelid swelling known as the Romaña sign. Other bite reactions include purpura; macular erythema; and vesiculobullous, papular, and urticarial lesions (Figure 2).² Associated lymphangitis or lymphadenopathy may be noted, and anaphylaxis has been reported. Similar to those of cockroaches, triatome antigens have been associated with atopic dermatitis and asthma.³

Chagas Disease Risk and Transmission

Triatomine reduviids are the primary vector of Chagas disease, and the geographic range of both continues to expand, particularly in North America. The disease remains endemic in Latin America, with the highest incidence now reported in Brazil.⁴ An estimated 240,000 to 350,000 individuals in the United States are infected, primarily immigrants from Mexico, Central America, and South America; approximately 30% of those infected will develop cardiac and/or gastrointestinal complications.⁴ If left untreated, Chagas disease leads to autonomic ganglion destruction and subsequent gastrointestinal and cardiac complications, including megacolon, dilated cardiomyopathy, and heart failure.⁵

Trypanosoma cruzi, the microorganism responsible for Chagas disease, is spread to humans through triatomine fecal matter scratched into the bite wound.⁶ Triatomine bugs have a highly developed gastrocolic reflex and defecate liberally as they feed. Fecal volume is heavily dependent on species and sex, with fifth-stage female nymphs producing the highest volume of excrement and thereby acting as particularly adept disease vectors.⁶ Triatoma infestans and members of the genus Mepraia are key vectors of T cruzi.¹ In areas of South America where populations of T infestans are controlled through public health measures, Mepraia emerge as a largely uncontrolled disease vector.^1,7 While endemic to the southern United States and South America, T cruzi has spread to much of North America and Europe by way of Triatominae as naturalized or invasive species.⁸

There are 3 phases of Chagas disease: acute, indeterminate, and chronic. A chagoma is a localized erythematous swelling at the site of the bite. The acute phase often lacks systemic symptoms but may include fever, myalgia, and headache. The intermediate phase may include fatigue and recurrent fevers. The most serious manifestations occur in the chronic phase and include cardiomyopathy with signs of congestive heart failure, irregular heartbeat, cardiac arrest, abdominal pain, constipation, and dysphagia.

Deforestation has been identified as a driving factor in the spread of Chagas disease, as the disease vectors shift from wilderness areas and animal hosts to inhabited areas where humans are the most readily available food source. Triatome bugs in areas experiencing higher levels of development or forest harvesting are forced into human-populated areas. As a result, instances of Chagas disease are on the rise in these communities.⁷ Salvador, Bahia, Brazil, has been identified as one such target of increased vector presence due to heavy deforestation, and the hottest months were identified as having the greatest threat of vector exposure.⁹ Brazil became the leading geographic area for the disease partly because of heavy loss of forested land.¹⁰

Vector Control and Prevention Strategies

Elimination of cracks and crevices in walls; replacement of wattle and daub with stucco, plaster, and other solid building materials; and the use of insecticides with durability in the environment have been used to reduce triatome bug infestation in homes. However, highly persistent insecticides carry greater environmental risk and may drive resistance as declining concentrations select for resistant arthropods. Repellents have less environmental impact and play an important role in vector control. Citronella essential oil has been observed to repel several species of triatome bugs that are common in Arizona; specifically, the component alcohols geraniol and citronellol were found to be effective at inhibiting triatome feeding.¹¹

Early detection of Chagas disease is essential, as end-stage cardiomyopathy and megacolon are difficult to treat. Newly developed multiantigen testing has shown promising results, suggesting a potential for more accurate testing for Chagas disease.⁸ Geospatial tracking and mapping of T cruzi vectors now are employed to track seasonal vector changes and disease patterns.⁹ Researchers also have developed a dedicated dichotomous key for the identification of triatome bugs endemic in Brazil with the hope of better identification and mapping of disease vector presence and density.¹⁰ The key consists of a series of statements with 2 choices in each step. It uses observable features of the arthropod to lead users to the correct identification.

Final Thoughts

Identification of triatome bugs can help with public health efforts to control the spread of disease. Patients with unilateral eyelid swelling should be evaluated for possible bedbug or triatome exposure.

Triatome bugs cause painful bites and serve as vectors for Chagas disease. In this article, we will address diagnosis and vector identification.

Key Morphologic Features

Insects from the subfamily Triatominae are identifiable by their long legs and a shieldlike abdomen behind a platelike pronotum that covers the thorax. Their half-membranous wings overlap, covering the central abdomen but leaving the lateral portions visible. Tigerlike stripes are characteristically prominent on the visible portions of the lateral abdomen. The stalklike head has an articulated beaklike mouth that can be retracted and used to deliver a powerful bite (Figure 1).

Feeding Mechanisms and Host Reactions

Triatome bugs are blood-feeding arthropods that hide in cracks and crevices in domestic structures by day and feed at night. They are shy feeders, and laboratory colonies have been known to die rather than feed in daylight. They are particularly common in thatched or wattle-and-daub dwellings, where they can be present in great numbers and descend on sleeping inhabitants at night. Triatome bugs require regular blood meals throughout the 5 developmental nymph stages in order to undergo successful molting.

In the wild, triatome bugs feed on a range of animals with little specificity, but in domestic settings they feed largely on humans. Thermosensors in the antennae help them locate blood vessels under the skin, which they penetrate easily due to their long mouthparts. Like other blood-sucking arthropods, they release an anticoagulant that facilitates continuous blood flow while feeding, which accounts for many of the cutaneous reactions observed after the host sustains a triatomine bite.¹

Triatomine bugs have trouble feeding through clothing and seek out exposed skin, particularly the eyelids, producing the characteristic unilateral eyelid swelling known as the Romaña sign. Other bite reactions include purpura; macular erythema; and vesiculobullous, papular, and urticarial lesions (Figure 2).² Associated lymphangitis or lymphadenopathy may be noted, and anaphylaxis has been reported. Similar to those of cockroaches, triatome antigens have been associated with atopic dermatitis and asthma.³

Chagas Disease Risk and Transmission

Triatomine reduviids are the primary vector of Chagas disease, and the geographic range of both continues to expand, particularly in North America. The disease remains endemic in Latin America, with the highest incidence now reported in Brazil.⁴ An estimated 240,000 to 350,000 individuals in the United States are infected, primarily immigrants from Mexico, Central America, and South America; approximately 30% of those infected will develop cardiac and/or gastrointestinal complications.⁴ If left untreated, Chagas disease leads to autonomic ganglion destruction and subsequent gastrointestinal and cardiac complications, including megacolon, dilated cardiomyopathy, and heart failure.⁵

Trypanosoma cruzi, the microorganism responsible for Chagas disease, is spread to humans through triatomine fecal matter scratched into the bite wound.⁶ Triatomine bugs have a highly developed gastrocolic reflex and defecate liberally as they feed. Fecal volume is heavily dependent on species and sex, with fifth-stage female nymphs producing the highest volume of excrement and thereby acting as particularly adept disease vectors.⁶ Triatoma infestans and members of the genus Mepraia are key vectors of T cruzi.¹ In areas of South America where populations of T infestans are controlled through public health measures, Mepraia emerge as a largely uncontrolled disease vector.^1,7 While endemic to the southern United States and South America, T cruzi has spread to much of North America and Europe by way of Triatominae as naturalized or invasive species.⁸

There are 3 phases of Chagas disease: acute, indeterminate, and chronic. A chagoma is a localized erythematous swelling at the site of the bite. The acute phase often lacks systemic symptoms but may include fever, myalgia, and headache. The intermediate phase may include fatigue and recurrent fevers. The most serious manifestations occur in the chronic phase and include cardiomyopathy with signs of congestive heart failure, irregular heartbeat, cardiac arrest, abdominal pain, constipation, and dysphagia.

Deforestation has been identified as a driving factor in the spread of Chagas disease, as the disease vectors shift from wilderness areas and animal hosts to inhabited areas where humans are the most readily available food source. Triatome bugs in areas experiencing higher levels of development or forest harvesting are forced into human-populated areas. As a result, instances of Chagas disease are on the rise in these communities.⁷ Salvador, Bahia, Brazil, has been identified as one such target of increased vector presence due to heavy deforestation, and the hottest months were identified as having the greatest threat of vector exposure.⁹ Brazil became the leading geographic area for the disease partly because of heavy loss of forested land.¹⁰

Vector Control and Prevention Strategies

Elimination of cracks and crevices in walls; replacement of wattle and daub with stucco, plaster, and other solid building materials; and the use of insecticides with durability in the environment have been used to reduce triatome bug infestation in homes. However, highly persistent insecticides carry greater environmental risk and may drive resistance as declining concentrations select for resistant arthropods. Repellents have less environmental impact and play an important role in vector control. Citronella essential oil has been observed to repel several species of triatome bugs that are common in Arizona; specifically, the component alcohols geraniol and citronellol were found to be effective at inhibiting triatome feeding.¹¹

Early detection of Chagas disease is essential, as end-stage cardiomyopathy and megacolon are difficult to treat. Newly developed multiantigen testing has shown promising results, suggesting a potential for more accurate testing for Chagas disease.⁸ Geospatial tracking and mapping of T cruzi vectors now are employed to track seasonal vector changes and disease patterns.⁹ Researchers also have developed a dedicated dichotomous key for the identification of triatome bugs endemic in Brazil with the hope of better identification and mapping of disease vector presence and density.¹⁰ The key consists of a series of statements with 2 choices in each step. It uses observable features of the arthropod to lead users to the correct identification.

Final Thoughts

Identification of triatome bugs can help with public health efforts to control the spread of disease. Patients with unilateral eyelid swelling should be evaluated for possible bedbug or triatome exposure.

The genus of flowering plants commonly known as prickly pear cacti (Opuntia) or sabra are native to the Americas but are naturalized in many parts of the world, particularly southwest Asia and Sicily, Italy, where they are grown commercially and commonly are seen growing on rocky hillsides. (Figure 1). A prickly pear cactus has paddles that represent modified stems, and the spines are modified leaves (Figure 2). Its bright red or yellow flowers, dark-red fruit, low water requirement, and adaptability to poor-quality soil make it an attractive plant for landscaping and an important agricultural crop in many parts of the world, including the United States, Mexico, and Southern Europe. The prickly pear fruit is tasty but loaded with seeds and often is eaten fresh or used to make jam. The paddles are sometimes cut into strips, breaded or battered, and fried. The spines are easily embedded in skin and are an important cause of dermatitis.

Identifying Features

Opuntia species are found in both warm and temperate zones and grow well in arid climates. Like other cacti, they are distinguished by their water-hoarding stems and glochids (needlelike modified leaves). In prickly pears, the stems flatten to leaflike paddles that alternate in direction. Photosynthesis occurs in the stem tissues, while modified leaves (spines) are purely for defense against predators and unsuspecting humans. Opuntia species are easily identified by their broad flattened stems and dark-red fruits, both of which bear glochids (Figures 3-5).

Dermatologic Implications of Prickly Pear Injury

Prickly pear spines are very small, sharp, and difficult to see. They embed in the skin in great numbers when the plant or its fruit are handled by unsuspecting humans and have a tendency to burrow into soft tissue and underlying structures. It is very difficult to remove prickly pear spines with forceps, and attempts to do so often drive them deeper into the skin.¹ Better results are obtained by tape stripping or using water-activated cosmetic pore strips.

Cactus spine injuries may lead to mucoceles of the oral mucosa and sinuses, especially in individuals who attempt to bite into the fruit without first scorching the spines with a blow torch.² Inflammatory responses to the embedded spines are common and often result in prolonged erythematous inflammatory papules at sites of injury. Recalcitrant dermatitis and edema of underlying tissues typically occur near the point of entry of a prickly pear spine and extend to areas where the spine migrates.^3,4 Individuals who casually brush up against the plant may not be aware that they have been inoculated with the spines and may not relate the prior accidental contact with the onset of erythematous papules and edema that occurs days later. Biopsy may reveal the prickly pear spines or a granulomatous reaction pattern within the dermis. Linear patterns of necrosis surrounded by palisading histiocytes may be noted, representing the tract of the inoculation injury.

If identified in tissue, glochids are variably refractile and measure 40 to 70 µm in diameter. Glochids initiate a delayed-type hypersensitivity and foreign body response. A T-helper 1 cytokine signal is typical, and there may be a secondary influx of neutrophils, but tissue eosinophilia is uncommon. Systemic inflammation also has been reported, including eosinophilic cholangitis without biliary stricture⁵ and septic and aseptic arthritis near the site of leaf puncture and at distant sites.^6,7 Allergic contact dermatitis has been reported due to contact with the fruit of the plant and can be confirmed by patch testing.^8,9

Potential Medicinal Benefits

Prickly pear cacti have shown potential medicinal properties. While the spines may produce intense inflammation when embedded in the skin, extracts of the fruit and leaf juices have shown anti-inflammatory properties. Various vesicle and polysaccharide extracts of Opuntia cacti have been shown to reduce environmental and chemical stressors associated with open wounds.^10-12 Preclinical studies also have suggested that they could be helpful in speeding the wound-healing process when applied topically. Opuntia species also have shown promise in reducing hyperpigmentation after topical application.¹³ Preliminary data in animals also have suggested that oral administration of the fruit may slow kidney deterioration in patients with diabetes.¹⁴ Following tissue penetration by the spines, Opuntia extracts have demonstrated the ability to prevent calcium deposition in soft tissue.¹⁵ Similar preliminary data also have suggested that Opuntia extracts may reduce toxicity from cadmium, chromium, methotrexate, and acetaminophen.^16-19 Extracts from the peel of the red pitaya (Hylocereus polyrhizus), a closely related cactus, have been studied for their potential to prevent the advance of alcohol-associated liver disease, suggesting that studies evaluating the benefits of prickly pear cacti and related species may be worth pursuing.²⁰

Final Thoughts

Prickly pear cacti have the potential to act as both friend and foe. The flowers and fruit are beautiful, and the plant is well adapted to xeriscape gardens in areas under perpetual water restriction. The fruit and flesh are edible if handled properly, and prickly pear jam is delicious. While the spines are capable of inflicting local injury and migrating to internal sites, causing arthritis and other deep tissue injury, extracts of the fruit and stems have potential uses for their anti-inflammatory effects and ability to protect against toxic injury. Further studies are needed to evaluate the therapeutic potential of Opuntia and related species.

The genus of flowering plants commonly known as prickly pear cacti (Opuntia) or sabra are native to the Americas but are naturalized in many parts of the world, particularly southwest Asia and Sicily, Italy, where they are grown commercially and commonly are seen growing on rocky hillsides. (Figure 1). A prickly pear cactus has paddles that represent modified stems, and the spines are modified leaves (Figure 2). Its bright red or yellow flowers, dark-red fruit, low water requirement, and adaptability to poor-quality soil make it an attractive plant for landscaping and an important agricultural crop in many parts of the world, including the United States, Mexico, and Southern Europe. The prickly pear fruit is tasty but loaded with seeds and often is eaten fresh or used to make jam. The paddles are sometimes cut into strips, breaded or battered, and fried. The spines are easily embedded in skin and are an important cause of dermatitis.

Identifying Features

Opuntia species are found in both warm and temperate zones and grow well in arid climates. Like other cacti, they are distinguished by their water-hoarding stems and glochids (needlelike modified leaves). In prickly pears, the stems flatten to leaflike paddles that alternate in direction. Photosynthesis occurs in the stem tissues, while modified leaves (spines) are purely for defense against predators and unsuspecting humans. Opuntia species are easily identified by their broad flattened stems and dark-red fruits, both of which bear glochids (Figures 3-5).

Dermatologic Implications of Prickly Pear Injury

Prickly pear spines are very small, sharp, and difficult to see. They embed in the skin in great numbers when the plant or its fruit are handled by unsuspecting humans and have a tendency to burrow into soft tissue and underlying structures. It is very difficult to remove prickly pear spines with forceps, and attempts to do so often drive them deeper into the skin.¹ Better results are obtained by tape stripping or using water-activated cosmetic pore strips.

Cactus spine injuries may lead to mucoceles of the oral mucosa and sinuses, especially in individuals who attempt to bite into the fruit without first scorching the spines with a blow torch.² Inflammatory responses to the embedded spines are common and often result in prolonged erythematous inflammatory papules at sites of injury. Recalcitrant dermatitis and edema of underlying tissues typically occur near the point of entry of a prickly pear spine and extend to areas where the spine migrates.^3,4 Individuals who casually brush up against the plant may not be aware that they have been inoculated with the spines and may not relate the prior accidental contact with the onset of erythematous papules and edema that occurs days later. Biopsy may reveal the prickly pear spines or a granulomatous reaction pattern within the dermis. Linear patterns of necrosis surrounded by palisading histiocytes may be noted, representing the tract of the inoculation injury.

If identified in tissue, glochids are variably refractile and measure 40 to 70 µm in diameter. Glochids initiate a delayed-type hypersensitivity and foreign body response. A T-helper 1 cytokine signal is typical, and there may be a secondary influx of neutrophils, but tissue eosinophilia is uncommon. Systemic inflammation also has been reported, including eosinophilic cholangitis without biliary stricture⁵ and septic and aseptic arthritis near the site of leaf puncture and at distant sites.^6,7 Allergic contact dermatitis has been reported due to contact with the fruit of the plant and can be confirmed by patch testing.^8,9

Potential Medicinal Benefits

Prickly pear cacti have shown potential medicinal properties. While the spines may produce intense inflammation when embedded in the skin, extracts of the fruit and leaf juices have shown anti-inflammatory properties. Various vesicle and polysaccharide extracts of Opuntia cacti have been shown to reduce environmental and chemical stressors associated with open wounds.^10-12 Preclinical studies also have suggested that they could be helpful in speeding the wound-healing process when applied topically. Opuntia species also have shown promise in reducing hyperpigmentation after topical application.¹³ Preliminary data in animals also have suggested that oral administration of the fruit may slow kidney deterioration in patients with diabetes.¹⁴ Following tissue penetration by the spines, Opuntia extracts have demonstrated the ability to prevent calcium deposition in soft tissue.¹⁵ Similar preliminary data also have suggested that Opuntia extracts may reduce toxicity from cadmium, chromium, methotrexate, and acetaminophen.^16-19 Extracts from the peel of the red pitaya (Hylocereus polyrhizus), a closely related cactus, have been studied for their potential to prevent the advance of alcohol-associated liver disease, suggesting that studies evaluating the benefits of prickly pear cacti and related species may be worth pursuing.²⁰

Final Thoughts

Prickly pear cacti have the potential to act as both friend and foe. The flowers and fruit are beautiful, and the plant is well adapted to xeriscape gardens in areas under perpetual water restriction. The fruit and flesh are edible if handled properly, and prickly pear jam is delicious. While the spines are capable of inflicting local injury and migrating to internal sites, causing arthritis and other deep tissue injury, extracts of the fruit and stems have potential uses for their anti-inflammatory effects and ability to protect against toxic injury. Further studies are needed to evaluate the therapeutic potential of Opuntia and related species.

The genus of flowering plants commonly known as prickly pear cacti (Opuntia) or sabra are native to the Americas but are naturalized in many parts of the world, particularly southwest Asia and Sicily, Italy, where they are grown commercially and commonly are seen growing on rocky hillsides. (Figure 1). A prickly pear cactus has paddles that represent modified stems, and the spines are modified leaves (Figure 2). Its bright red or yellow flowers, dark-red fruit, low water requirement, and adaptability to poor-quality soil make it an attractive plant for landscaping and an important agricultural crop in many parts of the world, including the United States, Mexico, and Southern Europe. The prickly pear fruit is tasty but loaded with seeds and often is eaten fresh or used to make jam. The paddles are sometimes cut into strips, breaded or battered, and fried. The spines are easily embedded in skin and are an important cause of dermatitis.

Identifying Features

Opuntia species are found in both warm and temperate zones and grow well in arid climates. Like other cacti, they are distinguished by their water-hoarding stems and glochids (needlelike modified leaves). In prickly pears, the stems flatten to leaflike paddles that alternate in direction. Photosynthesis occurs in the stem tissues, while modified leaves (spines) are purely for defense against predators and unsuspecting humans. Opuntia species are easily identified by their broad flattened stems and dark-red fruits, both of which bear glochids (Figures 3-5).

Dermatologic Implications of Prickly Pear Injury

Prickly pear spines are very small, sharp, and difficult to see. They embed in the skin in great numbers when the plant or its fruit are handled by unsuspecting humans and have a tendency to burrow into soft tissue and underlying structures. It is very difficult to remove prickly pear spines with forceps, and attempts to do so often drive them deeper into the skin.¹ Better results are obtained by tape stripping or using water-activated cosmetic pore strips.

Cactus spine injuries may lead to mucoceles of the oral mucosa and sinuses, especially in individuals who attempt to bite into the fruit without first scorching the spines with a blow torch.² Inflammatory responses to the embedded spines are common and often result in prolonged erythematous inflammatory papules at sites of injury. Recalcitrant dermatitis and edema of underlying tissues typically occur near the point of entry of a prickly pear spine and extend to areas where the spine migrates.^3,4 Individuals who casually brush up against the plant may not be aware that they have been inoculated with the spines and may not relate the prior accidental contact with the onset of erythematous papules and edema that occurs days later. Biopsy may reveal the prickly pear spines or a granulomatous reaction pattern within the dermis. Linear patterns of necrosis surrounded by palisading histiocytes may be noted, representing the tract of the inoculation injury.

If identified in tissue, glochids are variably refractile and measure 40 to 70 µm in diameter. Glochids initiate a delayed-type hypersensitivity and foreign body response. A T-helper 1 cytokine signal is typical, and there may be a secondary influx of neutrophils, but tissue eosinophilia is uncommon. Systemic inflammation also has been reported, including eosinophilic cholangitis without biliary stricture⁵ and septic and aseptic arthritis near the site of leaf puncture and at distant sites.^6,7 Allergic contact dermatitis has been reported due to contact with the fruit of the plant and can be confirmed by patch testing.^8,9

Potential Medicinal Benefits

Prickly pear cacti have shown potential medicinal properties. While the spines may produce intense inflammation when embedded in the skin, extracts of the fruit and leaf juices have shown anti-inflammatory properties. Various vesicle and polysaccharide extracts of Opuntia cacti have been shown to reduce environmental and chemical stressors associated with open wounds.^10-12 Preclinical studies also have suggested that they could be helpful in speeding the wound-healing process when applied topically. Opuntia species also have shown promise in reducing hyperpigmentation after topical application.¹³ Preliminary data in animals also have suggested that oral administration of the fruit may slow kidney deterioration in patients with diabetes.¹⁴ Following tissue penetration by the spines, Opuntia extracts have demonstrated the ability to prevent calcium deposition in soft tissue.¹⁵ Similar preliminary data also have suggested that Opuntia extracts may reduce toxicity from cadmium, chromium, methotrexate, and acetaminophen.^16-19 Extracts from the peel of the red pitaya (Hylocereus polyrhizus), a closely related cactus, have been studied for their potential to prevent the advance of alcohol-associated liver disease, suggesting that studies evaluating the benefits of prickly pear cacti and related species may be worth pursuing.²⁰

Final Thoughts

Prickly pear cacti have the potential to act as both friend and foe. The flowers and fruit are beautiful, and the plant is well adapted to xeriscape gardens in areas under perpetual water restriction. The fruit and flesh are edible if handled properly, and prickly pear jam is delicious. While the spines are capable of inflicting local injury and migrating to internal sites, causing arthritis and other deep tissue injury, extracts of the fruit and stems have potential uses for their anti-inflammatory effects and ability to protect against toxic injury. Further studies are needed to evaluate the therapeutic potential of Opuntia and related species.