Prednisolone is also given for 14 days. Seizures should be controlled with anticonvulsants.
Echinococcus granulosus (Taenia echinococcus) and hydatid disease
Dogs are the definitive hosts of the tiny tapeworm E. granulosus; ova pro- duced by the adult worms inhabiting the dog are ingested by intermediate hosts, which include sheep, cattle, camels and humans. The embryo is lib- erated from the ovum in the small intestine and invades the blood stream, spreading to the liver. The resultant cyst grows very slowly, sometimes inter- mittently, and may outlive the patient. It may calcify or rupture, giving rise to multiple cysts. The disease is common in the Middle East, North and East Africa, Australia and Argentina. Foci of infection persist in rural Wales and Scotland.
Clinical features
Hydatid disease is typically acquired in childhood; it causes cysts in the liver (75% of cases), lung, bone or brain. Symptoms are slow to develop and are a result of local pressure.
Investigations
USS or CT usually demonstrates the cyst. Serology is positive in 70% to 90% of cases.
Management and prevention
Surgical excision is the treatment of choice, with praziquantel administered peri- operatively to kill protoscolices. Albendazole should also be used, and may be combined effectively with aspiration. Good personal hygiene and animal handling practices, as well as deworming of dogs, can reduce dis- ease prevalence.
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Prednisolone is also given for 14 days. Seizures should be controlled with anticonvulsants.
Echinococcus granulosus (Taenia echinococcus) and hydatid disease
Dogs are the definitive hosts of the tiny tapeworm E. granulosus; ova pro- duced by the adult worms inhabiting the dog are ingested by intermediate hosts, which include sheep, cattle, camels and humans. The embryo is lib- erated from the ovum in the small intestine and invades the blood stream, spreading to the liver. The resultant cyst grows very slowly, sometimes inter- mittently, and may outlive the patient. It may calcify or rupture, giving rise to multiple cysts. The disease is common in the Middle East, North and East Africa, Australia and Argentina. Foci of infection persist in rural Wales and Scotland.
Clinical features
Hydatid disease is typically acquired in childhood; it causes cysts in the liver (75% of cases), lung, bone or brain. Symptoms are slow to develop and are a result of local pressure.
Investigations
USS or CT usually demonstrates the cyst. Serology is positive in 70% to 90% of cases.
Management and prevention
Surgical excision is the treatment of choice, with praziquantel administered peri- operatively to kill protoscolices. Albendazole should also be used, and may be combined effectively with aspiration. Good personal hygiene and animal handling practices, as well as deworming of dogs, can reduce dis- ease prevalence.
Fungal infections
Superficial fungal infections of the skin are described in Chapter 18.
Subcutaneous mycoses
ChromoblastomycosisChromoblastomycosis is a tropical fungal disease of the cutaneous and subcutaneous tissue. The usual cause is Fonsecaea pedrosoi, and the dis- ease is inoculated by trauma, particularly in those walking barefoot. Lesions may start several months after the injury in the form of a papule, which later turns into an irregular plaque. Later there may be hypertrophy of the tissue, leading to a characteristic cauliflower- like appearance.
Investigations
Biopsy shows pigmented, rounded sclerotic bodies. Culture confirms the aetiological agent.
Management
• Oral itraconazole or terbinafine. • Cryosurgery with liquid nitrogen.
Mycetoma (eumycetoma and actinomycetoma)
Mycetoma is a chronic suppurative infection of the deep soft tissues and bones, occurring mainly in the tropics. The limbs are most commonly affected. It is caused by either the filamentous fungus Eumyces (eumyce- toma, 40%) or by aerobic Actinomycetes (60%, actinomycetoma). Both groups produce characteristically coloured grains (microcolonies), the colour depending on the organism.
Clinical features
The causative organism is usually introduced by a thorn, and most com- monly affects the foot (Madura foot). Mycetoma begins as a painless swell- ing at the implantation site, which grows and spreads steadily within the soft tissues, causing further swelling and eventually penetrating bones.
Nodules develop under the epidermis and rupture, revealing sinuses through which grains are discharged. Deeper tissue invasion and bone involvement are less rapid and extensive in eumycetoma than in actinomy- cetoma. There is little pain and usually no fever or lymphadenopathy, but there is progressive disability.
Investigations
Biopsy/aspiration of pus should be sent for microscopy, culture and deter- mination of sensitivity.
Management
• Eumycetes: surgery plus ketoconazole or itraconazole. • Actinomycetes:
prolonged antibiotics—usually streptomycin and dapsone. • Surgical amputation may be required in severe cases.
Sporotrichosis
Sporotrichosis is caused by Sporothrix schenckii. It presents as a localised subcutaneous nodule at the site of inoculation (often a thorn scratch), which subsequently ulcerates with a pustular discharge (fixed cutaneous). The disease may then spread along the cutaneous lym- phatic channels, forming multiple cutaneous nodules that ulcerate and discharge (lymphocutaneous). Pulmonary involvement occurs but is rare.
Investigations
Biopsies should be sent for microscopy and culture.
Management
• Oral itraconazole for cutaneous and lymphocutaneous disease. • Ampho- tericin B for systemic life- threatening illness.
Systemic mycoses
AspergillosisThis is primarily respiratory and is described in Chapter 9.
Candidiasis
The species of Candida most commonly involved in human disease is C. albicans. Other species increasingly implicated are C. tropicalis, C. glabrata and C. krusei. Infection is most common in the immunosup- pressed, particularly neutropenic patients, as neutrophils form the body’s main defence against Candida. The source of infection is usually endog- enous, originating in flora in the patient’s oropharyngeal and genital areas, commonly producing oropharyngeal or vaginal candidiasis or ‘thrush’.
Systemic Candida infection may be acute or chronic:
Acute disseminated candidiasis: Usually presents as candidaemia, often in the presence of a central venous catheter. Recent abdominal surgery, antibiotics, total parenteral nutrition and IV drug misuse pre- dispose to candidaemia. Up to 40% have ophthalmic involvement, with
‘cotton wool’ retinal exudates progressing to vitreous haze and threat- ening sight.
Chronic disseminated (hepatosplenic) candidiasis: Presents in neu- tropenic patients as persistent fever despite antibacterial therapy. There is abdominal pain and elevated alkaline phosphatase, and multiple lesions are seen in the liver and spleen on imaging. This infection may last for months despite therapy.
Management
Infection detected on blood culture must be treated aggressively. In- dwelling catheters should be removed. Treatments for candidaemia include an echinocandin, amphotericin B, voriconazole and fluconazole.
Cryptococcosis
This is found worldwide and is caused by Cryptococcus neoformans and C. gattii. The former causes opportunistic infection, most commonly in those with HIV, whereas the latter causes severe disease in immunocom- petent hosts. Spread is by inhalation. Disseminated cryptococcal infec- tion mainly affects the immunocompromised. CNS manifestations include meningitis and cryptococcoma. Pulmonary cryptococcus can present as severe pneumonia in the immunocompromised, or as cavitating nodules in patients with lesser immunosuppression.
Diagnosis is by biopsy and/or culture. Treatment is with IV antifungal agents such as amphotericin B. Recovery may be monitored by a fall in antigen titres.
Mild pulmonary disease is treated with fluconazole or resection of nodules.
Other systemic mycoses affecting patients with severe immunosuppres- sion include fusariosis and mucormycosis. Both are rare but serious and require treatment with IV amphotericin B or posaconazole.
Histoplasmosis
Histoplasmosis is caused by Histoplasma capsulatum var. capsulatum and is found in all parts of the United States, especially in the east central states.
A variant, H. capsulatum var. duboisii, is found in parts of tropical Africa.
H. capsulatum multiplies in soil enriched by the droppings of birds and bats. Infection is by inhalation of infected dust.
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Clinical features
Histoplasma infection is usually asymptomatic or self- limiting. Pulmonary symptoms may include fever, nonproductive cough, pleuritic pain and an influenza- like illness. Erythema nodosum, myalgia and joint pain frequently occur. H. capsulatum var. duboisii usually spares the lungs, but can cause cutaneous ulcers and destructive bone lesions. On examination, lymphade- nopathy, hepatosplenomegaly, rashes and pulmonary crackles may be found.
Investigations
• Biopsy: tissue should be sent for smear, histology and culture. • CXR:
may show soft infiltrates, cavitating or calcified nodules and hilar lymphade- nopathy. • Antigen or antibody detection in blood.
Management
• IV amphotericin B in severe infection. • Itraconazole for chronic infection.
• Glucocorticoids may be added initially in severe pulmonary disease.
Coccidioidomycosis
This is caused by the airborne organisms Coccidioides immitis and C.
posadasii, and is found in Central and South America. It is acquired by inhalation and is asymptomatic in 60%. In others it affects the lungs, lymph nodes and skin. In immunocompromised patients, adrenal and meningeal spread occurs. Pulmonary coccidioidomycosis has two forms:
Primary coccidioidomycosis: If symptomatic, causes cough, fever, dyspnoea and rashes.
Progressive coccidioidomycosis: Systemic upset and lobar pneu- monia; may mimic TB. Diagnosis is by complement fixation and precipitin tests, and treatment is with antifungal azoles, or amphotericin B in severe disease.
Paracoccidioidomycosis
This is caused by Paracoccidioides brasiliensis and occurs in South America. Mucocutaneous lesions occur early. It affects the lungs, mucous membranes, skin, lymph nodes and adrenal glands. Treatment is with oral itraconazole.
Blastomycosis
This is caused by Blastomyces dermatitidis and occurs in parts of North America and occasionally in Africa. Systemic infection begins in the lungs and mediastinal lymph nodes and resembles pulmonary TB. Bones, skin and the genitourinary tract may also be affected. Treatment is with itracon- azole or amphotericin B.