Aquatic Skin Disorders

Chapter 82 Aquatic Skin Disorders

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The frequency of human contact with marine and freshwater aquatic environments is becoming more frequent. People travel to remote and exotic areas to participate in aquatic activities. When in these areas, be they for vacation or adventure, contact with aquatic animals, plants, and microbes are responsible for allergic reactions, trauma, infections, and envenomations. The dermatologic manifestations of many of these disorders are presented in this chapter.

Phytoplankton Dermatoses

This category of aquatic dermatoses includes diseases caused by algae, cyanobacteria, and dinoflagellates. Each of these organisms produces predictable disorders in aquatic life forms and humans. When phytoplanktons are “blooming,” they are able to cause a variety of dermatoses. Terminology defining these disorders can be ambiguous and misleading. Current taxonomy and genetic techniques are redefining and clarifying the exact nature and origins of these organisms, thus allowing more accuracy, less ambiguity, and better comprehension of disease states produced by phytoplankton.

The following vignettes attempt to differentiate organisms. Absolute separation of species is not possible, as chimerism is prevalent and gene sharing occurs.


Dinoflagellates are organisms common to all types of aquatic ecosystems. Approximately one-half of the species are photosynthetic;50 the remainder are heterotrophic and feed by phagotrophy and osmotrophy. Dinoflagellates are prominent members of the zooplankton and phytoplankton marine and freshwater ecosystems. Of the 2000 living species, more than 1700 are found in oceans and 220 in fresh water.134 These organisms are frequently and erroneously referred to as “algae,” because most are eukaryotic and derive energy by photosynthesis. Dinoflagellates exist as biflagellate unicells, plasmodia (i.e., multinucleated organisms), and coccoid stages.

Dinoflagellates are at their greatest concentration in temperate coastal waters, where they bloom in middle to late summer when sunshine and vertical stability allow aggregations to develop.134 In tropical waters and nutrient-poor temperate regions, all types of phytoplankton are generally scant. In polar waters, diatoms predominate over dinoflagellates.

About 75% to 80% of toxic phytoplankton species are dinoflagellates.31 When dinoflagellates “bloom,” “red tides” are produced and frequently kill fish and/or shellfish, either directly via toxin production or by clogging fish gills, depleting oxygen, etc.129 Colors of “red tides” vary from red to red-brown to brown. Anthropogenic and natural factors contribute to their development. Dinoflagellate toxins are some of the most potent biotoxins known. Accumulation in fish or shellfish produces diseases in humans like neurotoxic shellfish poisoning, paralytic shellfish poisoning, diarrheic shellfish poisoning, and ciguatera. “Blooms,” when aerosolized, produce cutaneous disorders in humans, such as dermatitis and urticaria (Figure 82-1).


The derivation of the term alga is from the Latin word for “seaweed.” Algae are a very large and diverse group of autotrophic, unicellular (microscopic), or multicellular (macroscopic) organisms. They are eukaryotic and therefore possess a nucleus enclosed within a membrane and membrane-bound chloroplasts (photosynthetic machinery derived from cyanobacteria).3 Phylogenetically, chloroplasts are membrane-bound organelles containing DNA similar to those of cyanobacteria. It is presumed that chloroplasts represent reduced cyanobacteria endosymbionts.3 Traditional terminology has used the terms algae and cyanobacteria synonymously and is currently regarded as outdated.3

The exact number of algae species is estimated to be 1 to 10 million and most are micro-algae.12 They are found in all parts of the earth, all waters both fresh and marine, the atmosphere, and soil. Microscopic forms suspended in the water column are designated phytoplankton. When conditions are present that facilitate proliferation, overgrowth occurs, resulting in “algal blooms.” Waters containing algal blooms become discolored, asphyxiate or poison surrounding aquatic life forms, and threaten the health of humans. Algae have been compared with plants but differ in many ways. For instance, algae are devoid of certain structures found in land plants, such as roots, leaves, stems, and vascular tissues.11 Plants and algae are photosynthetic. Algal photosynthetic pathways vary among different groups, some deriving energy from photosynthesis and uptake of organic carbon and others utilizing photoautotrophism.

Algal Dermatitis

Sargassum algae

Lyngbya Dermatitis

Lyngbya majuscula is an alga that produces tissue-damaging toxins. Direct contact with Lyngbya can result in serious skin reactions and tissue necrosis.


L. majuscula produces the dermatonecrotic toxins lyngbyatoxin A and debromoaplysiatoxin. Toxicity varies depending on season, type, and location of the algae.105 Not every strain of Lyngbya is toxic. It is the potency and/or concentration of these toxins against the skin that determines the degree of cutaneous damage.

Ciguatera Dermatitis

Epidemiology and Risk Factors

Ciguatoxin accumulates in predator fish, such as grouper, snappers, amberjacks, and barracudas. Ciguatoxin is produced by dinoflagellates, such as Gambierdiscus toxicus.142 The toxin is heat-resistant, so cannot be destroyed by cooking. Ciguatoxin-producing dinoflagellates are localized to tropical waters of the Caribbean and Pacific. Ciguatoxin is found in hundreds of species of reef fish.

Prototheca Species

Prototheca spp. are unicellular algae lacking chlorophyll. Protothecae spp. are often preliminarily misidentified as fungi in tissue and cultures. They are unicellular algae lacking chlorophyll. Prototheca spp. are infrequent causes of cutaneous and systemic infections.


There is no defined pharmacologic protocol for eradication of Prototheca. Protothecosis shows no tendency to self-heal. It is a chronic and progressive disease.70 Cutaneous lesions are cured with surgical excision. Amphotericin B has been used successfully.29 Prolonged treatments with the algaecidal agents ketoconazole, itraconazole, fluconazole, and miconazole have been reported effective.75,95,133

Human Pythiosis

The aquatic fungus-like organism Pythium insidiosum is a zoosporic plant pathogen and newly emerging human pathogen. P. insidiosum is a long-recognized plant pathogen causing seed decay and root rot of seedlings.47 The disease in humans and animals is called pythiosis.


Pythiosis is a cutaneous/subcutaneous disease of humans and animals. The organism is found in tropical, subtropical, and temperate areas of the world. Although primarily a cutaneous and intestinal disease of animals (horses, cats, dogs, and cattle), it is now an emerging human pathogen.47 Preferential ecologic niches are swampy environments, where the organism produces mobile biflagellate zoospores that are attracted chemotactically to traumatized human and animal tissues.71 The disease has been identified in the United States, Australia, Asia, South and Central America, and New Zealand.

Differential Diagnosis

Although not a true fungus, P. insidiosum has some morphologic characteristics in common with the order Zygomycetes. These similarities are best appreciated histologically. The fungi Zygomycetes are ubiquitous in nature, found in soil and decaying vegetation.

Hyphae of P. insidiosum species are broad, branched at right angles, usually nonseptate, and irregularly shaped with right-angled branching. They are described as ribbon-like (Figure 82-10, online).6 Fungi of the class Zygomycetes (e.g., Mucor, Rhizopus, and Absidia) are etiologic agents of a variety of infections in humans. Diseases caused by this group of fungi were formerly termed mucormycoses, but are now called zygomycoses.

The spectrum of zygomycosis includes cutaneous, gastrointestinal, renal, central nervous system, pulmonary, and rhinocerebral infections.6 Cutaneous zygomycosis has been associated with burns, traumatic wounds, surgical wound infections, contaminated dressings, and intramuscular injections.6 Cutaneous zygomycosis begins with erythema and induration, gradually evolving into a necrotic ulcer virtually identical to pythiosis. It is believed that many cases of pythiosis have been misdiagnosed as therapeutically nonresponsive zygomycosis.

Bacterial Infections

Aeromonas hydrophila

The Aeromonads are inhabitants of brackish and freshwater. Currently, four species of Aeromonas are recognized: hydrophila, caviae, salmonicida, and sobria. The spectrum of disease ranges from soft tissue infection to sepsis, and increasingly, diarrheal disease.


Aeromonas species are all usually sensitive to third-generation cephalosporins, carbapenems, and aztreonam. Fluoroquinolones are highly active against Aeromonas.137 Pertinent disease-producing Aeromonas species are resistant to penicillin and ampicillin. Resistance to trimethoprim, sulfamethoxazole, and tetracycline are increasingly being reported.78

Chromobacterium violaceum

The bacterium Chromobacterium violaceum rarely causes human disease, but can result in life-threatening sepsis with multiple metastatic abscesses. C. violaceum septicemia is clinically similar to melioidosis, the causative agent of which is Burkholderia pseudomallei.64 Microscopically, C. violaceum can be confused with vibrios.

Epidemiology and Risk Factors

C. violaceum is found in water and soil. It is abundantly present in the tropics and subtropics. Greater than three dozen cases have been reported in the United States, almost all from the southeast, primarily Florida.109,128 Infections occur primarily in the summer months. Cases have been reported from Africa, India, South America, and Australia.44,93 C. violaceum infects humans through exposure of nonintact skin to contaminated water and soil or after ingesting contaminated food or water.

Pseudomonas aeruginosa

In 1850, Sèdillot noted blue-green discharges on infected surgical dressings. In 1925, Osler defined the organism as an opportunistic or secondary invader of damaged tissue. The name aeruginosa derived from cultured organisms having the color of verdigris, that is, the rust of copper or brass. P. aeruginosa is one of the most serious sources of nosocomial bacterial infections.


P. aeruginosa is a ubiquitous, modal, non-fermentative, primarily aerobic, gram-negative rod.1,61 Ultrastructurally, P. aeruginosa possesses a polar flagellum and many surface pili. Virtually all strains produce an extracellular polysaccharide matrix necessary for biofilm formation.118,135 It is a fastidious organism that survives extremes of temperature, under hostile conditions and with minimal nutritional support. It infects humans, other vertebrates, animals, and plants. The infection is often associated with moist conditions or environs. Pseudomonas skin infections can follow exposure to hot tubs, swimming pools, and whirlpools (Figures 82-15 and 82-16). P. aeruginosa is the most common cause of skin disorders in occupational saturation divers and can occur after recreational use of diving suits.1,81


P. aeruginosa, although primarily a nosocomial pathogen, grows in a wide variety of environments with minimal nutritional components.100 It is commonly found in soil, water, and plants, but healthy humans and animals can be colonized. Up to 7% of healthy humans carry P. aeruginosa on their skin and in their nasal mucosa and throat. As high as a 24% fecal carriage rate has been reported.100

Hot Tub Folliculitis


This infection is seen most often following immersion in whirlpools or hot tubs, but can occur following swimming or scuba diving, both of which produce hyperhydration and maceration of the epidermis that predispose to Pseudomonas colonization and invasion. Numerous cases of “hot tub” or “whirlpool” dermatitis have been described.32,120,140 Eruptions can also occur after use of heated recreational water sources, such as swimming pools, water slides, and communal bath tubs. Contaminated bath toys, loofah sponges, moisturizing creams, and diving suits have been implicated as fomites in cases of Pseudomonas folliculitis.20,48,49,61

Green Nail Syndrome

Sep 7, 2016 | Posted by in EMERGENCY MEDICINE | Comments Off on Aquatic Skin Disorders
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