You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership If you are a member. Log in here
Newborn infants do not have teeth for about first 6 mo after birth (predentate period). At this stage, the upper and lower alveolar ridges in the mouth, also known as gum pads, house the primary (deciduous) and some permanent tooth buds. The primary dentition period starts with eruption of the first primary tooth; all 20 primary teeth erupt by 3 yr of age. The permanent teeth start erupting…
Disorders of organs outside the gastrointestinal (GI) tract can produce symptoms and signs that mimic digestive tract disorders and should be considered in the differential diagnosis ( Table 332.1 ). In children with normal growth and development, treatment may be initiated without a formal evaluation based on a presumptive diagnosis after taking a history and performing a physical examination. Poor weight gain or weight loss is…
You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership If you are a member. Log in here
Etiology Echinococcosis ( hydatid disease or hydatidosis ) is a widespread, serious human cestode infection ( Fig. 330.1 ). Two major Echinococcus groups of species are responsible for distinct clinical presentations. Echinococcus granulosus and related species cause cystic hydatid disease, and Echinococcus multilocularis causes alveolar hydatid disease . The adult parasites are small (2-7 mm) tapeworms with only 2-6 segments that inhabit the intestines of canines such…
Etiology Taenia solium, also known as the pork tapeworm , causes 2 different infections in children. In its normal life cycle, children can acquire the tapeworm form by ingestion of undercooked pork containing the larval cysts (see Chapter 328 ). In the intestines, the cyst converts into the tapeworm form. Children are also susceptible to infection by the eggs shed by tapeworm carriers. After the eggs…
Tapeworms are adult forms of cestodes , multicellular helminth parasites, that live in human intestines and cause non–life-threatening illness. Invasive larval forms of cestodes are associated with cysts that lead to severe human disease such as neurocysticercosis ( Taenia solium ; see Chapter 329 ) and echinococcosis (mostly Echinococcus granulosa and E. multilocularis ; Chapter 330 ). The adult worms themselves are flat and multisegmented, varying…
Several different trematodes , or flukes, can parasitize humans and cause disease. Flukes are endemic worldwide but are more prevalent in the less developed parts of the world. They include Schistosoma, or the blood flukes (see Chapter 326 ), as well as fluke species that cause infection in the human biliary tree, lung tissue, and intestinal tract. These latter trematodes are characterized by complex life cycles…
The term schistosomiasis (bilharzia) encompasses the acute and chronic inflammatory disorders caused by human infection with Schistosoma spp. parasites. Disease is related to both the systemic and the focal effects of schistosome infection and its consequent host immune responses triggered by parasite eggs deposited in the tissues. For the affected individuals, this frequently manifests as disabling chronic morbidity. Etiology Schistosoma organisms are the trematodes, or flukes…
Etiology Human trichinellosis (also called trichinosis ) is caused by consumption of meat containing encysted larvae of Trichinella spiralis, a tissue-dwelling nematode with a worldwide distribution. After ingestion of raw or inadequately cooked meat from pigs (or other commercial meat sources such as horses) containing viable Trichinella larvae, the organisms are released from the cyst by acid-pepsin digestion of the cyst walls in the stomach and…
Etiology Most cases of human toxocariasis are caused by the dog roundworm , Toxocara canis. Adult female T. canis worms live in the intestinal tracts of young puppies and their lactating mothers. Large numbers of eggs are passed in the feces of dogs and embryonate under optimal soil conditions. Toxocara eggs can survive relatively harsh environmental conditions and are resistant to freezing and extremes of moisture…
Onchocerciasis (Onchocerca Volvulus) Infection with Onchocerca volvulus leads to onchocerciasis or river blindness . Onchocerciasis occurs primarily in West Africa but also in Central and East Africa and is the world's 2nd leading infectious cause of blindness. There have been scattered foci in Central and South America, but the infection is now thought to be eliminated in the Americas. O. volvulus larvae are transmitted to humans…
Etiology The filarial worms Brugia malayi ( Malayan filariasis ), Brugia timori, and Wuchereria bancrofti ( bancroftian filariasis ) are threadlike nematodes that cause similar infections. Infective larvae are introduced into humans during blood feeding by the mosquito vector. Over 4-6 mo, the larval forms develop into sexually mature adult worms. Once an adequate number of male and female worms accumulate in the afferent lymphatic vessels, adult…
Etiology Strongyloidiasis is caused by the nematode, or roundworm, Strongyloides stercoralis. Only adult female worms inhabit the small intestine. The nematode reproduces in the human host by parthenogenesis and releases eggs containing mature larvae into the intestinal lumen. Rhabditiform larvae immediately emerge from the ova and are passed in feces, where they can be visualized by stool examination. Rhabditiform larvae either differentiate into free-living adult male…
Etiology The cause of enterobiasis, or pinworm infection, is Enterobius vermicularis, which is a small (1 cm in length), white, threadlike nematode, or roundworm, that typically inhabits the cecum, appendix, and adjacent areas of the ileum and ascending colon. Gravid females migrate at night to the perianal and perineal regions, where they deposit up to 15,000 eggs. Ova are convex on one side and flattened on the…
Etiology Trichuriasis is caused by the whipworm , Trichuris trichiura, a nematode, or roundworm, that inhabits the cecum and ascending colon. The principal hosts of T. trichiura are humans, who acquire infection by ingesting embryonated, barrel-shaped eggs ( Fig. 319.1 ). The larvae escape from the shell in the upper small intestine and penetrate the intestinal villi. The worms slowly move toward the cecum, where the…
Etiology Two major genera of hookworms, which are nematodes, or roundworms, infect humans. Necator americanus, the only representative of its genus, is a major anthropophilic hookworm and is the most common cause of human hookworm infection. Hookworms of the genus Ancylostoma include the anthropophilic hookworm Ancylostoma duodenale, which also causes classic hookworm infection, and the less common zoonotic species Ancylostoma ceylanicum (restricted mostly to Southeast Asia).…
Etiology Ascariasis is caused by the nematode, or roundworm , Ascaris lumbricoides. Adult worms of A. lumbricoides inhabit the lumen of the small intestine. The reproductive potential of Ascaris is prodigious; a gravid female worm produces 200,000 eggs per day. The fertile ova are oval in shape with a thick, mammillated covering measuring 45-70 µm in length and 35-50 µm in breadth ( Fig. 317.1 ). After passage…
Toxoplasma gondii, an obligate, intracellular, apicomplexan protozoan, is acquired perorally, transplacentally, or rarely parenterally in laboratory accidents, transfusions, or from a transplanted organ. In immunologically normal children, acute acquired infection most often is asymptomatic or unrecognized, but may cause lymphadenopathy or affect almost any organ. Once acquired, latent encysted organisms persist in the host throughout life. In immunocompromised persons, initial acquisition or recrudescence of latent organisms…
Babesiosis is a malaria-like disease caused by intraerythrocytic protozoa that are transmitted by hard body ( ixodid ) ticks. The clinical manifestations of babesiosis range from subclinical illness to fulminant disease resulting in death. Etiology More than 100 species of Babesia infect a wide variety of wild and domestic animals throughout the world. Only a few of these species have been reported to infect humans, including…