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The microorganisms that regularly infect patients with the acquired immunodeficiency syndrome (AIDS) have become well recognized. Most take advantage of defects in T-lymphocyte function, but others, such as Streptococcus pneumoniae and Haemophilus influenzae, take advantage of B-cell defects. Still others, such as Staphylococcus aureus and Shigella species, occur or persist for reasons that are unclear. Infections with organisms associated with hospitalization and medical procedures are also seen and should be anticipated. Among the infections taking advantage of T-cell defects, Pneumocystis carinii pneumonia is the most commonly diagnosed, but cytomegalovirus infection may be equally common. Disseminated Mycobacterium avium-intracellulare infection has been found in one half of our patients at postmortem examination. The retrovirus responsible for AIDS commonly infects the central nervous system, as does Toxoplasma gondii. Although candida infections are common, dissemination is uncommon. Many of the infections respond to appropriate therapy but tend to recur when treatment is stopped. Often treatment courses must be prolonged even beyond those used in other immunocompromised hosts.

Imported infectious diseases in the Departments for Epidemic Diseases in Blegdams Hospital and the University Hospital, Copenhagen, are reviewed for the period 1975-1986. A total of 3,454 cases were diagnosed. 92% were due to parasitic infections. 20.2% of the diagnoses were made i Danes. 38% of these had malaria. Ancylostomiasis, ascariasis and trichuriasis constituted 55% of the diagnoses and were found mainly in boat refugees from Vietnam. Africa, south of Sahara, Asia and the Mediterranean countries were the commonest sources of infection. The number of diagnoses increased tenfold as compared with the period 1965-1974 and this was due mainly to immigration of 3,000 boat refugees from Vietnam during the period 1979-1983. The number of danes averaged 57 annually. Only a slight increase occurred in imported infectious diseases in Danes as compared with the period 1965-1974. Malaria, bacterial and parasitic intestinal infections were the commonest diagnoses in this group. The next largest group of patients consisted of immigrants from Pakistan and Turkey. During the period 1979-1983, 79% of the diagnoses were made mainly in the boat refugees from Vietnam. The individual diseases are reviewed and the possibilities for prevention of imported disease are outlined.

Pentastomiasis is a parasitic zoonosis caused by pentastomes, members of an unusual phylum--Pentastomida--with characteristics of both arthropods and annelids. Adult pentastomes parasitize the respiratory tracts of reptiles or carnivorous mammals. The infection is generally limited to the tropics and subtropics, but ocular involvement has been reported in the southern United States. The majority of human pentastomiasis is caused by two species. The first, Armillifer armillatus, infects humans as secondary hosts. Infection is usually asymptomatic but has characteristic postmortem and radiologic features. The second, Linguatula serrata, can infect humans as does Armillifer or can cause a self-limited nasopharyngitis--the halzoun or marrara syndrome--with the human acting as a temporary definitive host. This article discusses the biology and parasitology of these metazoans as well as the clinical manifestations, pathology, diagnosis, and epidemiology of pentastomiasis.

A calcified nodule on the liver of a 62-year-old man from North Carolina, USA, contained a degenerated nymph of Linguatula serrata. The nodule was incidentally discovered at laparotomy for malignant lymphoma and cholelithiasis. The cuticle was all that remained of the parasite, but sclerotized openings and large spines on the cuticle proved the parasite was L. serrata, a pentastomid arthropod. Anatomic location and size of the parasite indicated that it was consistent with the nymphal stage of L. serrata. This is the fifth confirmed infection of humans from North America by a pentastomid parasite.

Intrasellar infection is characterized by pituitary dysfunction and damage to surrounding structures. In most cases patients have fever, headache, and visual disturbance and exhibit roentgenographic evidence of a mass. Suppurative infections may originate in the paranasal sinuses, meninges, or more distant foci and are commonest in the setting of preexisting pituitary adenomata. Pituitary tuberculosis may arise from hematogenous spread or extension of local lesions and may be confused with a variety of other granulomatous diseases. Congenital and acquired syphilis of the pituitary are more often diagnosed at autopsy or by the concurrence of pituitary dysfunction and serologic evidence of syphilis. Although viral infection may be associated with pituitary or hypothalamic dysfunction, overt hypophyseal infection is rarely documented. In contrast, a variety of parasites and fungi have been found in pituitary tissue. The diagnosis of pituitary infection should be considered when signs of intrasellar mass or pituitary dysfunction are accompanied by fever and other evidence of infection.

Substantial progress has been made in the last ten years in understanding the structural and functional organization of parasitic protozoa and helminths and the complex physiological relationships that exist between these organisms and their hosts. By employing the new powerful techniques of biochemistry, molecular biology and immunology the genomic organization in parasites, the molecular basis of parasite's variation in surface antigens and the biosynthesis, processing, transport and membrane anchoring of these and other surface proteins were extensively investigated. Significant advances have also been made in our knowledge of the specific and often peculiar strategies of intermediary metabolism, cell compartmentation, the role of oxygen for parasites and the mechanisms of antiparasitic drug action. Further major fields of interest are currently the complex processes which enables parasites to evade the host's immune defense system and other mechanisms which have resulted in the specific adaptations which enabled parasites to survive within their host environments. Various approaches in molecular and biochemical parasitology and in immunoparasitology have been proven to be of high potential for serodiagnosis, immunoprophylaxis and drug design.

Six cases of pharyngeal leech (identified as Myxobdella africana) are reported from a highland area of North Kenya. Three patients were severely anaemic and one died. There have been sporadic reports of leech infestation of man in East and Central Africa but these reports lack correct identification of the leech. This paper includes a detailed account of the systematics of the leech and of its habitat. The leeches were ingested accidentally by drinking water from two infested water sources. The major symptoms were a feeling of something in the throat, epistaxis and haemoptysis. On examination, pharyngeal blood was a consistent feature although the leech was rarely seen on initial inspection. Examination under anaesthesia was usually successful in locating and removing the leech. Prompt blood transfusion was life-saving in two cases. The water sources were used by both cattle and man; the cattle may also be parasitized by leeches. Methods of improving the water sources were discussed with community leaders.

Most parasites, by the nature of their continuous contact with the immune system, generate a prolific immune response. Unfortunately, much of this response is not protective, and some is harmful. Protective immunity in some infections is due to a combination of humoral and cellular immunity; in this circumstance parasites are coated with antibody which makes them susceptible to direct cytotoxicity by macrophages, eosinophils, and neutrophils. Antibody alone is protective against some other infections. Nonspecific and genetic factors are clearly important but are still undefined participants in the host response. The immune response may be pathogenic by inducing hypersensitivity, immunologically mediated fibrosis, or circulating immune complexes. Additionally, parasites have evolved unique ways of protecting themselves from the immune system, including altering their antigenic coat and inducing immunosuppression. Attempts to isolate "host-protective" antigens in parasitic infections may lead to effective vaccine development.