Textbook of Maritime Medicine

The skin is the human’s armour. It provides a relative protection against microorganisms, minor traumas, electricity and irritants and it represents the first line in the body’s response to infections. The skin is an organ in itself and consists of 3 layers: The epidermis is a stratified squamous epithelium composed of proliferating basal and differentiated suprabasal keratinocytes. The epidermis acts as the body's major barrier against an inhospitable environment. The top of the epidermis is the stratum corneum, a thin keratin layer of dead cells. The dermis contains blood and lymphatic vessels, nerves, sebaceous glands and sweat glands. The hypodermis consists mainly of fat and is separated from the underlying muscles by a tough fascia (Figure 10.3.1). Each of the three layers is subject to pathology from exogenous or endogenous afflictions. The skin is colonized with a variety of microorganisms that may become invasive in case of breaches in the skin barrier between the host and the environment.

Figure 10.3.1. Composition of the skin

It is not within the scope of this chapter to present a detailed overview of dermatology, but rather to describe some selected dermatological conditions that may occur in the maritime setting and interfere with the work aboard.

The vulnerability in the context of work of the outer surfaces of the body may manifest itself by of course be vulnerable in the context of work. In addition to contact dermatitis/eczema and other, diseases of the skin includinginclude infectious and neoplastic disorders. Skin conditions, or may also occur as part of a more generalized disease.

Little is known about the prevalence of skin diseases in seafarers. However, skin disorders were frequent in a Polish study [1]. An increased prevalence for dry skin, dermatitis, and acne found among Norwegian machine crew was found to be related to the exposure to oil and solvents although the latter was not significant [2]. Among fishermen, a questionnaire screening of 81 fishermen revealed a high percentage of dermatological conditions including histories on actinic keratosis (33%), actinic cheilitis (1%), basal cell carcinoma (19%), squamous cell carcinoma (9%), malignant melanoma (4%), eczema (37%), superficial fungal infections (30%), bacterial infections (58%), bites/stings (85%), and fish shocks (15%). On examination, actinic keratosis and cheilitis were present in 60% and 15%, respectively, and basal and squamous cell carcinoma in 9% and 6%, respectively [3].

Based on telemedical case logs, Lucas et al. have recently characterized the types of skin disorders occurring at sea that requires acute treatment. Out of a total number of 1.844 cases, 10% (n = 183) were for skin disorders. Sixty-eight percent (n = 125) were infections, 14% (n = 25) were inflammatory, 7% (n = 13) were environmental, and 11% (n = 20) were non-specific rashes. Cutaneous abscesses and cellulitis (n = 84) were the most common acute skin disorders encountered. In some cases digital photographs aided in the diagnosis [4]. 8% of the contacts to the Danish Radiomedical were due to skin disorders.

The work-related fraction of dermatological conditions have been reviewed by Lodde et al. [5]

10.3.1   Eczema, contact dermatitis and urticaria

Eczema is a non-contagious inflammation of the skin, characterized chiefly by redness, itching, and the outbreak of lesions that may discharge serous matter and eventually become encrusted and scaly. It represents a tissue reaction that is characteristic to many skin disorders but sometimes the term is used as a synonym for atopic dermatitis. In the current context dermatitis and eczema have identical meanings.

The vast majority of occupational skin diseases that may interfere with work manifest as contact dermatitis that may result from allergens or – in particular – irritating or corrosive external influences or a combination of the two. Due to the rather stereotypical character of skin reactions, allergic and irritative (also called toxic) contact dermatitis tendtends to look alike. Consequently, , and therefore it is not always easy to distinguish the two types of contact dermatitis. Both are itchy and both can be viewed in an acute phase with redness and frequently vesicle formation and oozing (Figure 10.3.2 and 10.3.3 ), and in a chronic phase characterized by hyperkeratosis and the development of fissures (Figure 10.3.4 ).

Figure 10.3.2 Acute contact dermatitis.

Figure 10.3.3 Acute contact dermatitis.

Figure 10.3.4 Chronic hand dermatitis.

But there are minor differences that may at times be of assistance when assessing the type of dermatitis. Irritative contact dermatitis can arise only where there has been an irritant exposure. Conversely, an allergic reaction may also be located beyond the contact area. Work-related contact dermatitis is mainly localized on the hands, since in most work the hands would be exposed to the prime contact with the causative agent. However, the hands can spread both irritating and allergenic exposures can be spread by the hands to other areas of skin areasthat are touched, typically the face. A facial contact dermatitis will otherwise suggest an influence from splashes from work materials or from an airborne agent in the form of gas, vapour or a solid/liquid aerosol (dust or droplets).

The generally accepted gold standard for an allergic contact dermatitis is the detection by patch test of a type IV allergic reaction (Figure 10.3.5). By extension, an allergic contact dermatitis tends to be excluded and to be interpreted as toxic if the patient’s skin does not respond to patch tests. But there are several sources of error. One cannot examine for an infinite number of potential allergens. Typically, the standard patch test includes approx. 20 allergens, but may be extended with additional selected substances of relevance to which the patient may have been exposed. But even then an allergy may not be recognized in case the relevant substance has not been identified among exposures and therefore has not been tested for. In addition, a positive reaction to the patch test needs not to be due to an allergic reaction. Despite dilution, patch testing with many substances will almost inevitably lead to an irritative reaction that may be misinterpreted as allergic. Furthermore, a demonstrated allergy does not necessarily represent the cause of the eczema. A subject allergic to nickel, for instance, can obviously obtain a new allergy to a substance that may not have been tested for, and will also not necessarily be protected to irritative reactions. Finally, testing with very potent allergens may result in sensitization by the testing procedure itself, and after testing one can subsequently speculate whether a positive reaction to patch testing was is in fact caused by exposure to the allergen, or whether the diagnostic investigation itself has resulted in sensitization. A positive reaction, therefore, does not necessarily mean that the eczema is allergic and caused by a specific substance. Nor does a negative reaction justify the conclusion that the eczema was concluding that it is irritative.

Figure 10.3.5 Patch test.

It is not normally a task for the occupational or maritime physician to perform patch testing, but rather to provide information on the exposures of potential relevance and to suggest the relevant contents of the test to the involved dermatologist. Therefore, the exposure story is important, and the practitioner in maritime medicine should recognize the potentially harmful exposures that may be of relevance in the maritime population in general and the specific exposures related to with certain tasks in particular. Examples of irritative exposures in the maritime setting include detergents in the galley, lubricants and cooling fluids in the engine room, the transported chemicals and oil products, and drilling mud on oil platforms. On fishing vesselsships, the irritative effects of fish may in themselves cause dermatitis. At the same time, however, allergic sensitisation to chemicals such as additives or to biological material may occur from the same exposures and give rise to allergic dermatitis. In the absence of knowledge about the exposures and their relevance one cannot plan patch testing or assess the significance of any positive and negative outcomes of patch testing.

To conclude, that the dermatitis is toxic demands not only that an allergic component has been excluded but also that an irritative exposure has been demonstrated. Irritation can be triggered by a chemical exposure to a variety of substances, in particular detergents, solvents, mineral oils, lubricating fluids and other substances that can affect and destroy the properties of the keratin layer of the skin. Interestingly, repetitive exposure to water can also frequently contribute to dry and irritated skin. Other irritative effects may be thermal, actinic or physical, e.g. by persistent friction on the skin. Dry irritated skin may also be induced by exposure to chemicals in powder form.

The skin-irritating properties of fish increases with the post-mortem age of the fish [6] and this may constitute a problem for fishermen, in particular when handling fish for fishmeal production. Dogger Bank itch reported from fishermen in European waters is a disabling allergic contact dermatitis caused by a metabolite produced by a marine Bryozoan [7, 8] (Figure 10.3.6 ).

Figure 10.3.6 Dogger Bank itch.

Contact urticaria (Figure 10.3.7) may be allergic or non-allergic. This and this reaction is related to angioedema, which occasionally – when located in the mouth or pharynx - may be a medical emergency. The allergic form (Type 1 allergy) may be related to contact with or ingestion of certain – in particular organic – substances such as including a variety of foods including fish (Figure 10.3.8), but also relate to toxins, e.g. form insect bites or infections. The non-allergic variety may relate to physical exhaustion or spurious mechanisms. In practice, it is difficult to identify the causing mechanisms for both types and it is also difficult to distinguish between them. Antihistamines usually provide rapid relief but, depending on its location, angioedema may demand more aggressive treatment with steroids and adrenaline.

Figure 10.3.7 Urticaria.

Figure 10.3.8 Allergic contact urticaria caused by exposure to fish.

The skin is not just equally resistant to external exposures in all individuals. Atopic subjects not only have an increased risk of developing airways allergy but they are also particularly prone to irritant contact dermatitis. In turn, they have a slightly less risk of allergic contact dermatitis. But as the presence of an irritant contact dermatitis will increase the possibilities for allergenic substances to penetrate the skin, both types of dermatitis may be present simultaneously. Atopic dermatitis is a constitutional dry skin, which is particularly frequent in children and young people. It is frequently accompanied by airway allergy. In atopic children and youth he dermatitis frequently manifests in the flexures (Figure 10.3.9), while hand dermatitis is the main problem in adults, in particular in combination with irritant exposure.

Figure 10.3.9 Flexural atopic dermatitis.

In addition to being vulnerable to particularly prone to irritative contact dermatitis, atopic subjects tend to be particularly prone to allergic immediate reactions in the skin such as contact urticaria. Atopic dermatitis is a constitutional dry skin, which is particularly frequent in young people that may develop eczema with the hands and flexures of the limbs as the main locations. It is frequently accompanied by airway allergy.

There is some evidence that the prognosis of skin disorders in young atopic subjects may be influenced by advice with regard to their future occupation. However, this type of pre-placement advice is currently not systematically implemented.

Patients with eczema should naturally be treated effectively. Cream is suitable for most conditions but ointment may be better with a chronic condition accompanied by with extreme dryness. There is a tendency in the public to be needlessly worried about the administration of topical steroid hormone because of the recognized side effects of these preparations. Patients with dermatitis should be explained that the side effects by refraining from treatment might well be even greater. The potency of local steroid treatment should not be larger than necessary, but on the other side sufficient for achieving quick recovery. Normally, one would require group two or three steroid for topical application. In the face, however, only group one steroid should be used. The intensive treatment should be continued for a few weeks after the dermatitis has disappeared after which the application intervals can be gradually decreased. It should be recognized that the skin might remain vulnerable for several months after the dermatitis has subsided even though the skin looks completely normal. During this time, it is essential that the skin’s moisture and lipid content is kept intact by continuous treatment with a humidifying cream. Therefore, care and prevention of relapse require patience and persisting care on all fronts, both when working on board and when at home ashore.
Obviously, it is important to reduce (for irritation) or eliminate (for allergies) the stimuli that triggered the eczema. Should this be a harmful exposure at work, the implication is not necessarily that the seafarer should be removed from the workplace or function. The technology may be substituted with a less harmful process or product, e.g. epoxy paint may be replaced by another type of paint, or an offending food product may be replaced in the galley. Frequently, a less aggressive hand cleansing and the introduction of skin care with a humidifying agent may suffice.

Skin protection A frequent and relevant secondary prevention will be protecting the skin by the use of gloves that should be suitable to the particular work is a frequent and relevant secondary prevention. Gloves. They should be kept intact and clean, and particular emphasis should be given to their inside. Similar to other personal protective equipment, the use of gloves should always be subsidiary to other preventive actions. Gloves can be unpleasant to use and may at times in themselves pose a security risk and cause skin problems. On the other hand much work on board would require the use of gloves as a primary preventive means in spite of their acknowledged side effects.

AllergicFrequent causes of allergic hand dermatitis from the use of gloves is frequently due to sensitization toinclude chrome that has been used for the tanning of-tanned leather gloves. Type 1 , and sensitization to latex gloves is a common cause ofcommonly causing contact urticaria. In addition, occlusion of the skin by gloves for several hours may in itself harm the skin, and in subjects with a tendency to hyperhidrosis or dyshidrosis the use of gloves may considerably worsen these conditions may worsen considerably by the use of gloves. Inner cotton gloves may reduce this problem. Barrier creams suitable to the exposure with some types for oils and solvents and others for water and detergents are recommended for primary as well as secondary prevention where gloves are not suitable. Common good hand hygiene should be promoted, and an appropriate moisturizer should be available for dry skin.

Other types of dermatitis

Seborrhoic dermatitis has many mostly unknown causes but is related to presence of the widely present yeast Malassezia furfur as well as to genetic, environmental, hormonal, and immune-system factors. It may be aggravated by illness or reduced general health, psychological stress, fatigue, and change of season. The seborrhoic eczema is a condition with dry or greasy peeling of the scalp, eyebrows, and face, and sometimes trunk (Figure 10.3.10). The condition is often related to dandruff. It is mostly harmless. A practical approach to treatment may be to first try different combinations of a dandruff shampoo, an antifungal agent and a topical steroid.

Figure 10.3.10 Seborrhoic dermatitis.

Stasis eczema (gravitational) results from insufficient venous return from the legs and is mostly associated with varicose veins (Figure 10.3.11). Compressive stockings or elastic dressing may prevent the stasis and topical steroid will reduce the dermatitis. Ulcers may complicate the condition.

Figure 10.3.11 Stasis eczema.

10.3.2   Psoriasis

Psoriasis is a chronic and frequently hereditary chronic skin disease caused by an excessively rapid growth of keratocytes. The disease usually presents with red, scaly patches present at all locations but most commonly on the knees and elbows. Psoriatic plaques may be frequently located on in the scalp, on the palms of hands and the soles, or on the genitals (Figure 10.3.12). Finger- and toenails are often affected and this location may cause misinterpretationmay be mistaken as fungal infestation (Figure 10.3.13). The disease may be recurrent or persistent. Symptoms can be controlled by topical steroid, and UV light and salty water is beneficial.

Figure 10.3.12 Psoriasis plaques on elbows.

Figure 10.3.13 Nail affection in poriasis

In some cases psoriasis is complicated by an inflammation in joints, and in particular axially along the spine and pelvic joints (Psoriatic arthritis). This complication may be serious and debilitating, and may require. It requires specialist treatment by rheumatologists.

In response to an irritant or other noxious exposure, patients with psoriasis are prone to develop a psoriatic response, in particular of the hands, as a so-called Köbner phenomenon (Figure 10.3.14)

Figure 10.3.14 Köbner phenomenon in psoriasis.

10.3.3   Acne

Acne vulgaris (commonly called acne) is a common skin disease, characterized by areas of skin with multiple non-inflammatory follicular papules or comedones and by inflammatory papules, pustules, and nodules in its more severe forms. Acne vulgaris mostly affects the areas of skin with the densest population of sebaceous follicles such as the face, the upper part of the chest, and the back (Figure 10.3.15). Severe acne may be inflammatory. Acne lesions are caused by androgenchanges that require androgen stimulation in the pilosebaceous units.

Figure 10.3.15 Acne.

Acne occurs most commonly during adolescence, affecting more than 96% of teenagers, but often continues into adulthood. In adolescence, acne is usually caused by an increase in male sex hormones, which people of both genders accrue during puberty. Acne mostly diminishes over time and tends to disappear or decrease in the early twenties. There is, however, no way to predict how long it will take to disappear entirely, and some individuals will carry this condition well into their thirties, forties and beyond.

Many different treatments exist for acne including benzoyl peroxide, antibiotics, retinoids, antiseborrhoic medications, salicylic acid, alpha hydroxy acid, azelaic acid, nicotinamide, and keratolytic soaps. The treatments aim to normalize shedding into the pore to prevent blockage, to kill Propionibacterium acnei, to reduce inflammation, and to provide hormonal manipulation.

10.3.4   Bullae and blisters

Bullae are fluid containing blisters larger than 5 mm in diameter (Figure 10.3.16). Bullous skin diseases may arise as autoimmune phenomena or due to external influence, e.g. second degree burns. Smaller blisters may form when the skin has been damaged by friction or rubbing, heat, cold or chemical exposure, but may also be due to infections such as herpes or varicella (Figure 10.3.17). Fluid collecting between the epidermis and the layers below cushions the tissue underneath, protecting it from further damage and allowing it to heal. Some blisters accompany infections and may be contagious.

Figure 10.3.16 Bullae.

Figure 10.3.17 Blisters in varicella.

10.3.5   Skin conditions caused by microorganisms

The skin is colonized by a variety of saprophytic microorganisms, some of which, however, may become invasive in case of skin lesions or with reduced immune resistance. Other microorganisms may infect the skin even with normal host resistance.

Fungi

The most important fungi that may cause skin symptoms include Trichophyton, Microsporium and Epidermophyton.

Tinea capitis afflicts the scalp, in particular in minors (Figure 10.3.18).. Tinea cruris is very common and causes an itching, red rash in the groins and perineum, in particular in men. Tinea corporis or ring worm may be caused by any dermatophyte that is transmitted from a human or an animal and starts with small pustules that eventually enlarge outwards and produce itchy patches with a more light coloured central area (Figure 10.3.19). Tinea cruris is very common and causes an itching, red rash in the groins and perineum, in particular in men (Figure 10.3.20).

Figure 10.3.18 Tinea capitis.

Figure 10.3.19 Tinea corporis.

Figure 10.3.20 Tinea cruris

Tinea pedis – athlete’s foot – is caused by several species of fungi most importantly Trichophyton. This is another very common mycosis presentspresenting with an itchy, red rash and scaling. Hyperkeratosis and fissure formation are frequently present in chronic cases. It is mainly seen in the lateral spaces between the toes. (Figure 10.3.21)Accompanying bullous id-reactions on the sole are common. In adults it is mostly accompanied by onychomycosis with discoloured, distorted and friable nails. (Figure 10.3.22) Tinea manuum is less frequent and mostly occurs in conjunction with tinea pedis. A unilateral palmar affliction may be misinterpreted as dermatitis in the absence of confirmative analyses for microfungi.

Figure 10.3.21 Tinea pedis.

Figure 10.3.22 Onychomycosis.

Topical antifungals are increasingly effective for treatment but onychomycosis may need long-term therapy.

Bacteria

Staphylococci (and streptococci) are the bacteria most often involved in skin infections. When a number of follicles are infected separately, a folliculitis ensues (Figure 10.3.23). When many closely situated follicles are infected concomitantly, a limited abscess – a furuncle – may develop (Figure 10.3.24).a furuncle). When many follicles are infected, a larger abscess may develop and form a carbuncle.

The highly contagious impetigo (Staphylococci or streptococci) is a superficial skin infection resulting in patches of honey coloured crusts and is mostly seen in children.

While folliculitis can be treated with topical or systemic antibiotics, a furuncle may and a carbuncle will require incision for evacuation of pus in addition to antibiotic treatment.

Figure 10.3.23 Folliculitis

Figure 10.3.24 Furuncle

A Dutch telemedical study has indicated an increasing incidence of skin infections between 2002 and 2006 (5.5% - 8.8%) and in the same period cases with features consistent with methicillin-resistant Staphylococcus aureus infections doubled from 36% to 74% [9]. The challenges related to methicillin resistance vary considerable worldwide with certain countries experiencing only few problems while resistance is a major public health issue in others. This difference is related to the practices related to the use of antibiotics. In this context it should be realized that a seafarer, who has been admitted to hospital abroad, might well import resistant strains of bacteria to his home country.

A strong red rash with well demarcated edges particularly in the face (Figure 10.3.25) or on the legs (Figure 10.3.26) accompanied by high fever, shivering and malaise signals an infection (erysipelas) with bacteraemia (streptococci). This condition needs medical attention and penicillin treatment.

Figure 10.3.25 Facial erysipelas.

Figure 10.3.26 Erysipelas of the lower limb.

Mycobacterium marinum infection may be acquired worldwide from contact with salty and fresh water in combination with skin trauma such as injuries from fish bites or fins or with existing scratches of the skin. A special risk has been reported for fishermen [10]. It extends from the skin to deeper layers such as tendons and may become debilitating if misinterpreted (Figure 10.3.27).

Figure 10.3.27 Mycobacterium marinum of the hand

Viruses

Many A host of viruses can cause skin symptoms. In this context, the two most common viral skin infections are is described.

Herpes simplex infection is a contagious skin condition. The primary infection frequently causes blisters in the face (Figure 10.3.28) and mouth (Figure 10.3.29). The virus hides in a nervous ganglion and may under certain circumstances (other diseases) travel along nerves and cause recurringreccurring blisters.

Figure 10.3.28 Herpes simplex.

Figure 10.3.29 Herpes simplex

Varicella zoster virus causes chickencausing chicken pox (mostly in childhood, but in many of the countries where seafarers are recruited also in late adolescents and adults [11]) (Figure 10.3.17). It latently resides in nerve ganglions adjacent to the spinal cord and may under special circumstances (other diseases) travel along the cutaneous nerves and cause painful blisters in the innervated skin territory – herpes zoster, whichand therefore often appear in a unilateral belt on the trunk (Figure 10.3.30). The pain may remain after disappearance of the blisters. Involvement of the eye region demands special attention to avoid damage to the cornea.

Figure 10.3.30 Herpes zoster

Herpes simplex and herpes zoster may be treated with topic anti-viral agents. In complicated cases systemic treatment may become necessary. Ointment with anaesthetics may prove helpful in herpes zoster.

10.3.6   Infestations

Scabies

Scabies is caused by the mite Sarcoptes scabies, variety hominis. The characteristic symptoms of scabies infection include superficial burrows, intense pruritus, a generalized rash and secondary infection. S-shaped tracks in the skin are often accompanied by small, insect-type bites called nodules that may look like pimples. These burrows and nodules are often located in the crevices of the body, such as the webs of fingers, toes, feet, buttocks, elbows, waist area, genital area and axilla. The intense itching and rash is caused by an allergic reaction of the body to the burrowed mites. The rash can be found over much of the body, especially in immune-compromised people (HIV positive or elderly); the associated itching is often most prevalent at night. Secondary impetigo may occur after scratching (Figure 10.3.31). 

 

Figure 10.3.31 Scabies..

The allergic symptoms of itching and rash are caused by tissue reaction that develops over time, to the mites and their by-products under the skin. In individuals that have never before been exposed to scabies, the onset of clinical signs and symptoms is 2–6 weeks after infestation. In previously exposed individuals, onset can be as soon as 1–4 days after infestation.

Scabies is highly contagious and can be spread by scratching, picking up the mites under the fingernails and simply touching another person's skin. They can also be spread onto other objects like keyboards, toilets, clothing, towels, bedding, and furniture onto which the mite may be rubbed off, especially if a person is heavily infested.

The parasite mostly does not survive longer than two or three days away from human skin. In particular, crowded facilities on board may favour the transmission of scabies throughout an entire crew by skin-to-skin contact with an infected person. Transmission is also likely between bed partners. Washing clothing in very hot water and dry on high heat will help prevent the transmission. Permetrin sprays can be used for items that cannot be laundered.

Signs and symptoms of early scabies infestation mirror those of other skin diseases, including dermatitis, syphilis, allergic reactions and infestation with other ectoparasites such as lice.

Generally, the diagnosis is made by the identification of burrows (Figure 31). This may be difficult because they are scarce and obscured by scratch marks. If burrows are not found in the primary areas that are likely to be affected, the entire skin surface of the body should be examined.

Topical Permetrin 5% is the drug of choice and is applied to the skin before bedtime and left on for about 8 to 14 hours, then showered off in the morning. There is some evidence that a 10% sulphur ointment in petroleum jelly applied topically is effective. It is cheap and readily available without a prescription.

An outbreak on board a ship should focus on preventing re-infection. All close contacts should be treated at the same time, even if asymptomatic. Cleaning of the environment should occur simultaneously and include treatment of furniture and bedding, vacuuming floors, carpets and rugs, mopping and disinfecting floor and bathroom surfaces by mopping, cleaning the shower after each use and daily washing in hot water of recently worn clothes, towels and bedding and then drying in high heat and/or steam ironing.

Lice

Pediculosis is an infestation of lice –lice -- blood-feeding ectoparasites. "Pediculosis" in humans refers to lice infestation of any part of the body, and may be divided into the following types: Pediculosis capitis, corporis and pubis (Crabs).

Infestation with Pediculus humanus capitis is most frequent on children and their families. Lice are spread through direct head-to-head contact with an infested person. From each egg or "nit" may hatch one nymph that will grow and develop to the adult louse. While feeding on blood by piercing the skin with their mouthparts they excrete saliva, which irritates the skin and causes itching.

To diagnose infestation, the entire scalp should be combed thoroughly with a louse comb and the teeth of the comb should be examined for the presence of living lice after each time the comb passes through the hair.

No product or method assures 100% destruction of the eggs and hatched lice after a single treatment. However, there are a number of treatment modalities that can be employed with varying degrees of success. These methods include chemical treatments, natural products, combs, shaving, hot air, and silicone-based lotions.

Pediculus humanus humanus (the body louse) is indistinguishable in appearance from the head louse but body lice attach their eggs to clothes, whereas head lice attach their eggs to the base of hairs.

Body lice infestations can spread rapidly under crowded living conditions where hygiene is poor but is unlikely to persist on anyone who bathes regularly and who has at least weekly access to freshly laundered clothing and bedding.

Body lice are spread through prolonged direct physical contact with an infested person or through contact with articles such as clothing, beds, bed linens, or towels that have been in contact with an infested person. Body lice are a nuisance in themselves and cause intense itching. They are however, also vectors of other diseases (epidemic typhus, trench feverepidemic typhus, trench fever, and louse-borne relapsing feverrelapsing fever).

Nits (eggs) are generally easy to see in the seams of an infested person’s clothing, particularly around the waistline and under armpits. They are oval and usually yellow to white in colour and may take 1-2 weeks to hatch.

An infestation with body lice should be treated by improving the personal hygiene. Clothing, bedding, and towels used by the infested person should be laundered using hot water. A pediculicide is generally not necessary if hygiene is maintained and items are laundered appropriately at least once a week.

Crabs

Crab lice (also known as "crabs" are parasitic insects notorious for infesting human genitals (Phthiriasisphthiriasis pubis) but they may also live on other areas with hair, including the eyelashes. They feed exclusively on blood (Figure 10.3.32).

Figure 10.3.32 Crab lice.

The main symptom is itching in the pubic-hair area, resulting from hypersensitivity to louse saliva, which can become stronger over two or more weeks following initial infestation. In some infestations, a characteristic grey-blue or slate coloration appears (maculae caeruleae) at the feeding site, which may last for days.

Pubic lice usually infect a new host only by close contact between individuals, usually through sexual intercourse. As with most sexually transmitted pathogens, they can only survive a short time away from the warmth and humidity of the human body.

Because of the strong association between the presence of pubic lice and classic sexually transmitted infections. Therefore patients diagnosed with pubic lice should undergo evaluation for other sexually transmitted diseases.

A pubic louse infestation is usually diagnosed by carefully examining pubic hair for nits, nymphs’ nits, and adult lice.

Crab lice can be treated by applying Permetrin 1% cream rinse or pyrethrins to the affected areas and washing off after 10 minutes. Shaving off or grooming any hair in the affected areas with a fine-toothed comb is necessary to ensure full removal of the dead lice and nits. A second treatment after 10 days is recommended. Bed sheets should be changed and be put away in a plastic bag, without air and well shut. They should be left alone for 15 days before washing to avoid the reproduction and survival of lice eggs that may have been left on the sheets and lead to reinfestation.

Cockroaches

Cockroaches are frequent type 1 sensitizers in ships, especially those sailing in the tropics. In addition to airways symptoms they may be related to dermatitis [12]. The clinical significance remains unclear.

10.3.7   Malignant tumours

Both spinocellular carcinoma and malignant melanoma can be triggered by external influences, especially from radiation with the sun's ultraviolet exposure playing the dominant role. This explains the increased occurrence in the maritime population of cutaneous malignancies such as malignant melanoma and skin carcinoma [13, 14]. Excess solar radiation also accounts for an increased prevalence of spinocellular carcinoma of the lip in fishermen [15] and seafarers [13]. Those with previous dermatological cancers and continued solar exposure should be controlled for recurrence and advised accordingly [16].

10.3.8   Other skin conditions that may affect seafarers

Prickly heat is caused by excessive sweating in combination with relatively occluded sweat glands resulting in minor slightly itchy blisters that may breakbrake and result in scaling. It is a frequent but completely benign condition that does not require treatment.

Sunburn is another trivial but, however, potentially dangerous condition that is frequent among seafarers. In addition to malignant consequences, ultraviolet radiation may cause phototoxic and photoallergic reactions [17]. Most physicians are aware of adequate protection to UV-radiation (sunscreens, covering clothes, avoiding direct sunlight exposure and outdoor activities during midday hours, and practicing progressive exposure). It is, however, important that advice is actually given to seafarers in risk. There is a particular threat to fair-skinned seafarers and those with a history of previous skin cancer or with compromised immunoresistance [16].

Dermatoses caused by marine organisms are frequently seen worldwide. Cutaneous injuries after exposure to marine environments include bacterial and fungal infections and lesions caused by aquatic plants and protists. Some of disease outcomes are well known, such as Vibrio vulnificus septicaemia and erysipeloid, but others are uncommon, such as envenomation caused by ingestion or contact with certain dinoflagellates or cyanobacteria, which are associated with rashes that can begin within minutes after exposure [18]. Although these conditions are more frequent in the tropics, they may also occur in temperate environments. In tropical countries, a high proportion of fresh water fishermen are likely to be infected by the parasite Onchocerca volvolus that in addition to “river blindness” causes skin nodules and itching [19].

Many marine/aquatic invertebrates, such as sponges, cnidarians, echinoderms, crustaceans, and molluscs, are associated with different kinds of dermatologic lesions that can vary from irritant or allergic contact dermatitis to physical trauma and envenomation. These cutaneous lesions may result in mild local reactions or can be associated with severe systemic reactions [18].

Invertebrate animals, such as cnidarians, sea urchins, and worms, and aquatic vertebrates, such as venomous fishes and stingrays, are commonly associated with skin lesions in many countries, including occupational dermatoses among fishermen. The presence of unusual lesions and a report of contact with an aquatic environment should alert the physician to the aetiology of the cutaneous problems [18].

Reference

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