Hookworm is a common intestinal nematode infection caused by _Necator americanus_ (New World hookworm) and _Ancylostoma duodenale_ (Old World hookworm). Symptoms include abdominal pain, diarrhea, loss of appetite, weight loss, fatigue, and anemia.

Hookworm

_Ascaris lumbricoides_ is a widespread nematode and the largest intestinal parasite found in humans, with females reaching lengths exceeding 1 meter. Although it is now relatively uncommon in the United States, it is common globally and can cause symptoms ranging from a mild cough and abdominal pain to severe complications like intestinal obstruction and impaired growth.

*Ascaris lumbricoides*

The pinworm, caused by _Enterobius vermicularis_, is the most prevalent nematode infection in the United States. It typically causes nighttime sleeplessness and intense itching around the perianal area, where female worms migrate to lay their eggs during the night.

*Enterobius vermicularis*

_Necator americanus_, also known as the New World or North American hookworm, is a nematode parasite that causes hookworm infection. Symptoms of infection include abdominal pain, diarrhea, appetite and weight loss, fatigue, and anemia.

*Necator americanus*

*Toxocara canis* and *T. cati* are the causative nematodes for toxocariasis infections, which can be transmitted from dogs/cats to humans. 

 *Toxocara canis* and *T. cati*

_Trichinella spiralis_ is the parasitic nematode that causes trichinellosis (or trichinosis). It is contracted by eating undercooked meat containing larvae, which are released in the body and encyst within muscle tissues. Symptoms include fever, muscle pain, and digestive issues, while severe cases can result in coordination loss, respiratory or cardiac difficulties, and death.

*Trichinella spiralis*

_Dirofilaria immitis_ is the nematode parasite responsible for heartworm disease in dogs and other animals. Transmitted through mosquito bites, the infection manifests with fatigue and coughing, and can lead to death if left untreated.

*Dirofilaria immitis*

_Ancylostoma duodenale_, also known as the Old World hookworm, is a species of parasitic nematode that causes hookworm infection in humans. Symptoms include abdominal pain, diarrhea, loss of appetite, weight loss, fatigue, and anemia.

*Ancylostoma duodenale*

Whipworm (*Trichuris*) is a parasitic nematode that can infect both humans and dogs. Globally, it is a significant public health concern, causing infections in approximately 604 to 795 million people.

*Trichuris*

- _Ascaris lumbricoides_
- _Necator americanus_
- _Ancylostoma duodenale_
- _Enterobius vermicularis_
- _Toxocara canis_ and _T. cati_
- _Trichinella spiralis_
- _Dirofilaria immitis_

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Roundworms, belonging to the phylum Nematoda, are unsegmented worms with a complete digestive system. While they are found in various environments, many species are common intestinal parasites that are frequently transmitted through undercooked foods.

Roundworms (Nematodes)

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Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

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