Chapter VI.32. Parasites: Protozoans and Helminths
Cali E. McAllister
Loren G. Yamamoto, MD, MPH, MBA
June 2022

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A 2 year old boy in a refugee camp is treated for dehydration secondary to vomiting and foul diarrhea. After rehydration, the staff suspects that he might have short segment Hirschsprung disease based on his history and growth pattern. He is flown to your hospital for surgical evaluation. He is obviously malnourished and underweight, but he improves clinically. After eating lunch, the boy vomits and the nurses note the presence of several large worms in the vomitus. They later note that he has a visible worm in his stool. A stool sample is sent for ova and parasite analysis which identifies Giardia cysts and Ascaris eggs. He is treated with albendazole which covers both the Giardia and Ascaris.


Protozoans and helminths are the two main subgroups of eukaryotic parasites. Both groups are less prevalent in the United States and more prevalent in low- and middle-income countries. Many of them require fecal-oral transmission or vectors (insects and rodents) but can also gain entry through sexual contact, inhalation, or direct contact (1). Understanding the mechanism of entry of these parasites enables prevention of infection. Proper public health measures, which are taken for granted in the U.S., are responsible for minimizing our exposure to these infections. These measures include regulations and laws ensuring clean water, agriculture and livestock, proper food handling, sanitation (sewage and trash disposal), vector control (insects and rodents), and housing. Other lifestyle factors including good nutrition, footwear and skin care also reduce the risk of infection.

Protozoans are single-cell organisms that depend on their host for energy source (2). Many species have evolved transmission routes and exploit environmental advantages to increase their chances of host contact. While not all parasitic protozoa have sexual cycles, all protozoa (unlike helminths), reproduce asexually in the human host. Protozoans can be classified into amoebas, flagellates and sporozoans (2). Pneumocystis used to be considered a protozoan, but it is now classified as an opportunistic fungus. The presenting symptoms of each protozoan infection is dependent on the niche or where in the body the infection is harbored.

The main disease-causing amebas include Entamoeba histolytica, Balantidium coli, and Naegleria fowleri (1). Amebiasis is caused by E. histolytica and classically presents with bloody diarrhea (amebic dysentery), but it may also present with nonspecific gastroenteritis, edema, failure to thrive, or an amebic liver abscess. The diagnosis can be made by visualizing organisms in the stool or by antigen detection, but PCR tests are preferred due to their high sensitivity and specificity and ability to differentia E. histolytica from other amebas. B. coli is not endemic to the U.S. or Hawaii but has many reservoir hosts that are present here, including domestic and wild animals. Dysentery is the main symptom of B. coli infection except in persons living with HIV where the parasite can affect other sites besides the GI tract (2). N. fowleri is the cause of a rare and fatal infection also called primary amebic meningoencephalitis (PAM). Naegleria live in warm and hot springs and, other fresh water sources, so most infections are acquired by swimming or diving in hot springs. Naegleria organisms enter the body often through the nose and cribriform plate causing rapid infection of the central nervous system resulting in encephalitis. Symptoms include frontal headache, vomiting, and confusion, followed by coma and death. Other sources include tap water used in backyard water slides, whirlpool baths, and Neti pots (used for home nasal irrigation, with warm tap water. Effective treatment is lacking but sources mention efficacy with amphotericin B, azithromycin, fluconazole, miltefosine, and rifampin (3).

Flagellates include giardia, trichomonas, trypanosomes, and leishmania. Giardia duodenalis (formerly known as G. lamblia and G. intestinalis) causes diarrhea, malabsorption and abdominal discomfort. Giardia organisms are generally not seen in stool samples, and Giardia cysts are only occasionally found in the stools. Giardia organisms were most commonly diagnosed by having the patient swallow a gelatin capsule containing a string (the so-called string test) which was then retrieved and analyzed by microscopy; however, this has been largely replaced by various techniques that detect Giardia antigen or DNA in stool specimens. Giardia can be treated with tinidazole, metronidazole, and nitazoxanide (4).

Trichomonas vaginalis is a sexually transmitted motile protozoan which causes vaginitis. Clinically, a pruritic vaginal discharge results, with or without dysuria (2). Motile protozoans can be seen on a microscopy wet mount of the vaginal discharge. Males are often asymptomatic. Nucleic acid amplification tests (NAATs) are highly diagnostic but expensive. Patients of are often treated empirically with metronidazole or tinidazole (5).

Trypanosomiasis can be of the African or the American type. African sleeping sickness is caused by Tryp. brucei rhodesiense and Tryp. brucei gambiense, which are both spread by the biting of the tsetse fly vector (2). Symptoms of infection include fever, headache, malaise, rash, and lymphadenopathy; spontaneous remission, or coma and death may follow (1). CNS involvement typically occurs 1 to 2 years after the initial infection with significant neurologic dysfunction. Treatment options include melarsoprol, eflornithine, suramin, and corticosteroids (6).

American trypanosomiasis (also known as Chagas disease) is caused by Tryp. cruzi which is spread by the reduviid bug. Initial presentation is often with a swollen eye and cheek, called a chagoma or Romaña sign, followed by malaise, fever, and lymphadenopathy (1). Some patients improve clinically without treatment but develop chronic infection. 20% to 40% of patients develop heart of GI complications such as cardiomyopathy, dysrhythmias, megacolon, and megaesophagus. Treatment options include benznidazole and nifurtimox (7).

Leishmania infections are transmitted by sandfly vectors and are primarily zoonotic infections (2). Leishmania donovani causes visceral leishmaniasis (also known as kala-azar) which presents as fever, malaise, lymphadenopathy, organomegaly, anemia and weight loss (2). Leishmania tropica and many other species can cause cutaneous leishmaniasis (also known as uta) which results in a small red papule that can form a painless, large, ulcerated lesion with an indurated border (2). Leishmania braziliensis and twenty other species of leishmania are capable of causing mucocutaneous leishmaniasis (also known as espundia) (1). Symptoms of mucocutaneous leishmaniasis include necrotizing inflammation in the skin, mucous membranes, and cartilage that can cause destruction of the skin and permanent damage to the surrounding tissues (2).

Sporozoans include cryptosporidium, plasmodium, and toxoplasma. Cryptosporidium may be a contaminant in bodies of water. It is resistant to chlorination, but many home filtration systems will filter out the cysts (1). Infection with cryptosporidium results in self-limited diarrhea in healthy persons (no treatment required), but in immunocompromised individuals, it may cause fever, chronic diarrhea, weight loss, and death (1).

Malaria is caused by the various Plasmodium species (ovale, vivax, falciparum, malariae, knowlesi) (2). Malaria is a complex infection which is described in a separate chapter. It is transmitted by anopheles mosquito vectors and it can be prophylaxed and treated with antimalaria medications. Rarely, malaria can be transmitted through blood transfusion or from an infected pregnant person to their baby. Antimalarial treatment depends on the Malaria species and resistance patterns. Agents include chloroquine, hydroxychloroquine, quinine, primaquine, tafenoquine, mefloquine, doxycycline, clindamycin, atovaquone-proguanil, artemether-lumefantrine, and artesunate-mefloquine (8).

Toxoplasma gondii is harbored by cats (2). Infection can be acquired by exposure to cat feces (by touch or through contaminated food) and accidental ingestion of infectious oocysts. Most healthy adults have an asymptomatic or a non-specific illness similar to infectious mononucleosis. Infection in pregnant mothers during early gestation puts the fetus at risk of congenital toxoplasmosis which may result in brain injury, microcephaly, hydrocephalus and chorioretinitis (2). Immunocompromised patients may develop chorioretinitis and focal brain lesions. Treatment options include pyrimethamine and sulfadiazine (9).

Parasitic helminths that infect humans include the two phyla Nematoda (roundworms) and Platyhelminthes (flatworms). Infection by parasitic helminths is usually by consuming contaminated food or water although other forms of transmission include infected soil and vectors such as mosquito, deer fly, and black fly. Once they gain entry to the human host, infective larvae can spread throughout the human body and cause different syndromes; most will return to the GI tract and mature into adult worms. Since many of these organisms are gastrointestinal, common presentation patterns include gastroenteritis, failure to thrive, weight loss, edema, and or abdominal discomfort. The immune system has a difficult time eradicating protozoans and parasites. Eosinophilia is often associated with parasitic infections, but eosinophilia is only seen during the invasive phase of worms (1).

Trematodes (also called flukes) are unsegmented flatworms which include the groups fasciola, clonorchis, paragonimus, and schistosoma (2). Intestinal flukes include Fasciolopsis buski found in Asia. Clonorchis sinensis (the Asian liver fluke) is acquired by eating raw or undercooked freshwater fish. Fasciola hepatica (another liver fluke) is found in sheep-raising areas and infection is acquired by accidentally eating organisms in contaminated produce. Paragonimus westermani is a lung fluke found in Asia and Africa. It is acquired by eating contaminated shellfish.

Schistosomes are classified as blood flukes because they spread through the blood circulation. These organisms can penetrate the skin directly when the individual is exposed to contaminated water (e.g., by swimming or drinking). Schistosoma species include S. mansoni, S. japonicum, S. mekongi, S. guineensis, and S. intercalatum cause intestinal symptoms. S. haematobium causes bladder symptoms including bladder carcinoma. The treatment drug of choice for schistosomiasis is praziquantel (10).

Cestodes (also called tapeworms) are segmented flatworms (2). Taenia solium is the pork tapeworm and Taenia saginata is the beef tapeworm. Humans can acquire the infection when ingesting undercooked pork and beef meat containing cysts, when ingesting food contaminated with eggs shed by an infected person, or by autoinfection (1). In most instances, intestinal infection with adult tapeworms will result (taeniasis). In few cases, when the infecting organism is T. solium, it can migrate to other organs (cysticercosis) including the eye or brain resulting in focal brain lesions, often leading to seizures (neurocysticercosis). Neurocysticercosis is common in countries where livestock raising conditions are not well regulated and undercooked pork is consumed. The southern U.S. regions encounter frequent cases of neurocysticercosis in immigrants from Mexico. Treatment options include albendazole and praziquantel (11).

Dipylidium caninum is a tapeworm highly prevalent among dogs and cats in the U.S. and can infect children that accidentally swallow an animal’s infected flea (which acts as the intermediary host); proglottids (parts or a segment of the tapeworm that resembles a grain of rice) are then shed in the stool but children remain otherwise mostly asymptomatic. This is infection self-limited, clearing spontaneously in most instances. Treatment options include praziquantel (12).

The fish tapeworm, Diphyllobothrium latum, is found in undercooked freshwater fish and is the longest parasite to infect humans, often reaching 25 meters in length (1). This organism has largely been eliminated from previously endemic areas in Minnesota (the land of lakes) and the Great Lakes. Raw salmon (salmon sushi), trout, and pike ingestion may be a source of D. latum infections. Although salmon are salt water fish they may acquire D. latum infection when they return to freshwater and some salmon populations are land locked in fresh water lakes. Symptoms of D. latum infection are not obvious in the early stages of infection but can eventually lead to B12 deficiency anemia, watery diarrhea, fatigue, and mechanical obstruction of small bowel (2). Treatment options include praziquantel and niclosamide (both off label) (12).

Nematodes are nonsegmented, roundworm groups that are tapered at both ends and differ from tramatodes and cestodes by their complete digestive system (2). They can be remembered by the mnemonic NEMATODES (with 3 As and 3 Ts).These stand for Necator, Enterobius, mosquito borne (Wuchereria and Brugia), Ascaris, Ancylostoma, Angiostrongylus, Trichuris, Trichinella, Toxocara, Onchocerca, Dracunculus, Eye worm (Loa loa), and Strongyloides. They infect humans via ingestion (EATT: Enterobius, Ascaris, Trichuris, Trichinella) or by skin penetration (SAN: Strongyloides, Ancylostoma, Necator). Although the method of transmission varies among nematodes, the most common nematode infections in children are the soil transmitted helminths which include A. lumbricoides, T. trichiura, and hookworm (N. americanus and A. duodenale) (2).

Necator americanus and Ancylostoma duodenale are hookworms which are endemic in warm, moist climates. N. americanus is endemic in the southeast U.S. (1). Larvae in the soil attach (hook) between the toes and penetrate the skin (causing dermatitis), migrate into the bloodstream, and the lungs causing eosinophilic pneumonia (Löffler syndrome). Organisms migrate into the airway, and are coughed up and swallowed reentering the GI tract. Finally, they attach (hook) to the intestinal wall where they mature to adult worms and cause a chronic infection often manifesting as iron deficiency anemia. Treatment options include albendazole, mebendazole, pyrantel pamoate (13).

Angiostrongylus cantonensis (rat lungworm) is a parasitic nematode that is found in many tropical and subtropical regions including Hawaii. Although this parasite has many intermediate hosts, humans often become infected by consuming slugs or snails from unwashed fruits or vegetables. The initial symptoms include a prodromal gastrointestinal phase that can progress to neuroangiostrongyliasis (NAS). The common symptoms of NAS include headache, nausea/vomiting, paresthesia, and dysesthesias. The infection is often suspected by the finding of eosinophilic meningitis (14). Definitive diagnosis of NAS is by lumbar puncture and PCR testing. Treatment is still being researched but may include corticosteroids, antiparasitic drugs (such as albendazole), and local symptomatic treatment such as lidocaine (15).

Enterobius vermicularis (pinworms) are the most common parasites in the U.S. Many children have this infection at some point, even though many may remain asymptomatic. Spread likely occurs among young children in group settings (e.g., preschool). These worms are small (about 0.7 cm long), usually found in the perineal area resembling moving pieces of shiny white thread (2). Pinworms naturally reside in the rectum of young children, exit the anus and lay eggs at night when the child is asleep, then reenter the anus. It is this migration, in and out, that causes pruritus. A perianal sample can be obtained by applying sticky tape or an adhesive plastic paddle to the anus several hours after the child has fallen asleep (1). Alternatively, visual inspection at night will often discover the worms. In girls, the worms may enter the vagina instead of the anus, and cause dysuria or vaginal pruritus. This is a complaint commonly encountered in emergency departments at night. If the parent brings the child in early, the moving worms are usually still visible in the perineal area. If the parent brings the child in late, dead degenerating worms may be visible in the perineum. Otherwise, a chief complaint of sudden onset of dysuria or vaginal discomfort in the absence of urinalysis evidence of a urinary tract infection, is suggestive of pinworms. These can be eradicated with a single dose of pyrantel pamoate or mebendazole, which can be repeated in two weeks to reduce the likelihood of reinfection 16,17).

Ascaris lumbricoides is one of the most common parasitic worms in the world as it prevails wherever poverty occurs (2). If you see a large intestinal worm (about 30 cm or 12 inches long), odds are this is what it is. They are large and pink resembling smooth earthworms. Ascaris worms survive and grow in the intestine. Infection may be asymptomatic or they may grow in large enough numbers to cause bowel obstruction. Newly hatched larvae may migrate throughout the body into the liver, heart and lungs. Eosinophilic pneumonia (Löffler syndrome) is caused by migrating ascaris larvae as they invade the lungs. Hepatobiliary ascariasis can occur in children with large worm burden and may cause cholecystitis, cholangitis, hepatic abscess, pancreatitis, and death (2). Ascariasis in the placenta may cause neonatal ascariasis. Treatment options include albedazole, mebendaole, and pyrantel pamoate (18).

Mosquito borne nematodes include Wucheria bancrofti, Brugia timori, and Brugia malayi which all cause elephantiasis by blockage of lymphatic vessels (also known as filariasis). Elephantiasis presents with lymphedema of the arms, legs, breasts, and genitalia (2). Tropical Pulmonary Eosinophilia is a common cause of restrictive lung disease of young men in India caused by filariasis (1). Other forms of filariasis includes Loa loa (an African eye worm, which is spread by the Chrysops fly vector) and Onchocerca volvulus (also known as river blindness), which is spread by the Simulium blackfly. Loa loa requires a different treatment regimen than the other causes of filariasis and it is crucial that this infection is ruled out before treating W. bancrofti or O. vovulus infections. With Loa loa infections, treatment is first started with albendazole and then diethylcarbamazine (DEC) once microfilariae levels decrease to below 8000 microfilariae per mL (19). If you were to treat Loa loa the same way as the other forms of filariasis, by just starting DEC, that may lead to treatment associated encephalopathy and possible blindness of the patient. Other treatment options include ivermectin, albendazole, doxycycline, and moxidectin (19,20).

Dirofilarias are small parasites transmitted by mosquito bites. D. immitis is also known as heartworm and while mostly a parasite of dogs and other mammals it can occasionally infect humans; since humans are an accidental host, the worm dies off and shows only as a solitary nodule or granuloma on a chest radiography without further symptoms (rarely as eosinophilia). Antiparasitic treatment is not needed for D. immitis (1).

Trichuris trichiura (whipworm) is found in tropical regions. The infestation can be asymptomatic or manifest with the usual GI chronic infestation symptoms (1,21). Trichinella spiralis is the pork roundworm, which is acquired by eating poorly cooked contaminated pork. The larvae initially cause regular GI infestation symptoms, but as maturing worms lay new eggs, these larvae hatch and migrate into the bloodstream where they lodge in muscle tissue forming calcifications which cause fever and myalgia (1,22). Toxocara canis and Toxocara cati are dog and cat parasites which, when infecting humans, may be asymptomatic or cause the syndrome of visceral larvae migrans.(1,23)

Dracunculus medinensis is known as the Guinea worm. Larvae infecting tiny aquatic crustaceans can be accidentally ingested by unknowingly drinking contaminated fresh water. Over time, adult worms will grow in the subcutaneous tissue to nearly one meter long, and emerge through the skin to lay eggs. There is no known effective medication and worms classically must be physically removed through the skin by gradually, and slowly (about 1 cm per day), pulling them (rolling them onto a stick). Due to actions from the World Health Organization started in 1986, cases of dracunculiasis are now only found in southern Sudan as the disease has been nearly eradicated from the rest of the world (1).

Strongyloides stercoralis (threadworm) is another parasite that enters the body through exposed feet stepping over contaminated soil. It then passes through the lymphatic system to the heart and lungs where it travels up the airway and down into the intestines via the upper GI tract. Autoinfection can also occur. Symptoms are often mild unless the person is immunocompromised, in which case it can present with protracted watery diarrhea or systemic dissemination (hyperinfection syndrome) (1).

Albendazole is a drug which covers a broad range of parasitic infections. Mebendazole and pyrantel pamoate are older drugs that are also highly efficacious. Many parasites are susceptible to albendazole and pyrantel pamoate. Metronidazole and tinidazole have activity against many protozoans. Smilarly, nitazoxanide has activity against Giardia and Cryptosporidium. Diethylcarbamazine is used for filariasis parasites. Praziquantel works for most flatworms (flukes and tapeworms). Ivermectin can be used for strongyloidiasis and onchocerciasis, among others. Some parasitic infections do not benefit from treatment. It should be noted that this chapter is written for general background information only. Therapeutic decisions should be based on more comprehensive information describing each infection type. The purpose of this summary is to provide a general educational overview. Note that treatment details, doses and durations are not provided here. Please use a current authoritative reference for clinical therapeutic decisions (e.g., the AAP Red Book).

Summary of Protozoans and Parasites [Route of infection in brackets].
I. Protozoans
   A. Ameba
     1. Entamoeba histolytica [fecal-oral]
     2. Naegleria fowleri [hot springs]
   B. Flagellates
     1. Giardia duodenalis (also known as G. lamblia) [fecal-oral, contaminated water]
     2. Trichomonas vaginalis [sexually transmitted]
     3. Trypanosomes
       a. Tryp cruzi [reduviid bug vector]
       b. T. rhodesiense, T. gambiense [tsetse fly vector]
     4. Leishmania [sandfly vector]
   C. Sporozoans
     1. Cryptosporidium [drinking water]
     2. Plasmodium [anopheles mosquito vector]
     3. Toxoplasma [cat feces, contaminated food]
II. Trematodes (flukes)
   A. Intestinal: Fasciolopsis buski [fecal-oral]
   B. Liver
     1. Clonorchis sinensis [raw freshwater fish],
     2. Fasciola hepatic [sheep-raising area, contaminated agriculture]
   C. Lung: Paragonimus westermani [shellfish]
   D. Blood: Schistosoma [skin penetration in contaminated water]
III. Cestodes (tapeworms)
   A. Beef: Taenia saginata [ingesting contaminated undercooked beef]
   B. Pork: Taenia solium [ingesting contaminated undercooked pork]
   C. Fish: Diphyllobothrium latum [ingesting infected raw freshwater fish]
IV. Nematodes (roundworms):
   A. Necator [fecal-oral, skin penetration]
   B. Enterobius [fecal-oral]
   C. Mosquito borne
     1. Wucheria bancrofti [mosquito vector]
     2. Brugia malayi [mosquito vector]
   D. Ascaris [fecal-oral]
   E. Ancylostoma [fecal-oral, skin penetration]
   F. Trichuris [fecal-oral]
   G. Trichinella [poorly cooked pork]
   H. Toxocara [dog and cat feces]
   I. Onchocerca: river blindness [Simulium blackfly vector]
   J. Dracunculus: Guinea worm [contaminated water]
   K. Eye worm: Loa loa [Chrysops fly]
   L. Strongyloides: threadworm [fecal-oral, skin penetration]


Questions
1. Name two parasites which are associated with the ingestion of uncooked freshwater fish?
2. What is the most common parasitic worm in American children?
3. Name a parasite associated with the ingestion of poorly cooked pork?
4. Name two motile (flagellated) protozoan infections commonly found in the U.S.
5. Name two types of hookworms.
6. Name four protozoans and two parasites transmitted by mosquito vectors.
7. Name 3 or 4 protozoans and parasites that are transmitted by biting flies.
8. Name 2 or 3 protozoans and parasites that invade the brain.
9. Name two parasitic infections that can be passed transplacentally


References
1. Despommier DD, Griffin DO, Gwadz RW, et al. Parasitic Diseases. 7th ed. 2019 Parasites Without Borders, Inc. New York, NY.
2. Cornelissen CN, Hobs MM. Lippincott Illustrated Reviews: Microbiology. 4th edition, 2020, Wolters Kluwer, Philidelphia, PA.
3. Amebic Meningoencephalitis and Keratitis. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:193-196.
4. Giardia dueodenalis (formerly Giardia lamblia and Giardia intestinalis) Infections. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:335-338.
5. Trichomonas vaginalis Infections. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:777-781.
6. African Trypanosomiasis. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:781-783.
7. American Trypanosomiasis. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:783-786.
8. CDC Centers for Disease Control and Prevention. Treatment of Malaria: Guidelines for Clinicians (United States). https://www.cdc.gov/malaria/diagnosis_treatment/clinicians1.html, accessed 1/31/2023
9. Toxoplasma gondii Infections. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:767-775.
10. Schistosomiasis. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:666-668.
11. Tapeworm Disease (Taeniasis and Cersticercosis). In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:744-747.
12. Other Tapeworm Infections. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:747-750.
13. Hookworm Infections. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:421-422.
14. Clinical Subcommittee* of the Hawaii Governor’s Joint Task Force on Rat Lungworm Disease. “Preliminary Guidelines for the Diagnosis and Treatment of Human Neuroangiostrongyliasis (Rat Lungworm Disease) in Hawaii.” Disease Outbreak Control Division, State of Hawaii, Department of Health, August 29, 2018. https://health.hawaii.gov/docd/files/2018/08/RLWD_Preliminary_Clinical_Guidelines_FINAL_082918.pdf accessed 1/31/2023.
15. Cucueco, K., Bathen, K., & Fischberg, D. (2020). Lidocaine Infusion for Refractory Pain from Rat Lungworm Disease - Honolulu, Hawai'i. Hawaii J Health Soc Welfare. 2020;79(8):246–248.
16. Drugs for Treatment of Parasitic Infections. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:949-989.
17. Pinworm Infection. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:.
18. Ascaris lumbricoides Infections. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:.
19. Lymphatic Filariasis. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:490-492.
20. Onchocerciasis. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:550-552.
21. Trichuriasis. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:780-781.
22. Trichinellosis. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:775-777.
23. Toxocariasis. In: Committee on Infectious Diseases, Kimberlin DW, Barnett ED, Lynfield R, Sawyer MH (eds). 2021-2024 Red Book: Report of the Committee on Infectious Diseases, 32nd edition. 2021, American Academy of Pediatrics, Itasca, IL. pp:766-767.


Answers to questions
1. Diphyllobothrium latum (fish tapeworm), Clonorchis sinensis (Asian liver fluke),
2. Pinworms (Enterobius vermicularis).
3. Trichinella spiralis (trichinosis), Taenia solium (cysticercosis).
4. Trichomonas vaginalis, Giardia duodenalis.
5. Ancylostoma duodenale, Necator americanus
6. Malaria (Plasmodium vivax, falciparum, ovale, malariae, knowlesi), filariasis (Wucheria bancrofti, Brugia malayi).
7. Tryp cruzi (reduviid bug vector, which is not really a fly, but it is a biting bug), T. rhodesiense and T. gambiense (tsetse fly vector), leishmania (sandfly vector), Onchocerca (Simulium blackfly vector), loa loa eye worm (Chrysops fly).
8. Taenia solium (neurocysticercosis), Naegleria fowleri, Toxoplasma gondii, Loa loa (eye), Angiostrongylus cantonensis
9. Trypanosoma cruzi (Chagas disease), Toxoplasma gondii (toxoplasmosis), Plasmodium spp (malaria)


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