Malaria, Schistosomiasis, Threadworm, Trichinosis, Hookworm, Whipworm PDF

Summary, Malaria In humans, it is caused by 5 species of protozoa The protozoa has an (complex) indirect life cycle. Mosquitoes in the genus Anopheles are vectors and are also the definitive hosts. Malaria can also be transmitted horizontally by blood transfusions and even vertically due to sequ...

Summary, Malaria In humans, it is caused by 5 species of protozoa The protozoa has an (complex) indirect life cycle. Mosquitoes in the genus Anopheles are vectors and are also the definitive hosts. Malaria can also be transmitted horizontally by blood transfusions and even vertically due to sequestration of parasites in the placenta. Malaria is most common in sub-Saharan Africa but at one time was common almost worldwide (wherever the mosquito vectors were present). People living in endemic areas can develop a form of immunity termed premunition. Vaccines are emerging to prevent malaria. Antimalarial drugs are available. Symptoms of malaria typically develop 10 – 15 days after the bite of an infected mosquito although symptom onset can be delayed for months. Malaria (Overview) Causal Agent: Plasmodium Falciparum Type of Organism: Protozoan Where is it Most Prevalent: Sub Saharan Africa Mode(s) of Transmission: Biological Vector HOSTS Definitive: Mosquitos Intermediate: Humans Others: Primates Organs or Tissues Infected: Red blood cells Symptoms: Fever and chills Primary Avoidance Tactic(s): Prophylaxis, bugspray ____________________________________________________________________________ Summary, Snail Fever (Human Schistosomiasis)  It is caused by flukes Transmission in humans is by direct penetration. These trematodes have complex life cycles with snails serving as the only first (intermediate) hosts. Most widely distributed of the human split worms. Most infections occur in sub-Saharan Africa. The estimated worldwide prevalence is about 82 million people. Humans can slowly develop immunity to infection. No vaccines are currently available. Some species of split worms cause swimmer's itch, at times a frequently encountered non-contagious disease in Michigan. Human Schistosomiasis Overview Causal Agent: Schistosomes Type of Organism: Fluke Where is it Most Prevalent: Africa and Brazil Mode(s) of Transmission: Direct penetration HOSTS Definitive: Human Intermediate: Freshwater snail Others: Organs or Tissues Infected: Liver and bladder Symptoms: Fever, chills, headache, itch Primary Avoidance Tactic(s): Stay out of water that schistosomes are in ____________________________________________________________________________ Summary, Human Threadworm Disease (Strongyloidiasis) It can auto-infect its hosts, and maintain free living populations indefinitely as well as parasitic populations indefinitely. Direct life cycle Transmission is fecal-oral, and direct penetration Most people remain non-symptomatic, and infections can last for decades without them ever noticing it The human threadworm is so unusual because of 3 aspects of their biology: It can maintain multiple generations as a parasite and as a free-living parasite Worms are passed in feces instead of eggs This parasite can auto-infect its hosts. No other parasitic worms do it, although pinworms come close (retroinfection). Human threadworms regurgitate these microbes throughout the tissues of the host, often leading to local infections/bacteremia, followed by general sepsis. Such clinical sequelae are often fatal. Strongyloidiasis (Human Threadworm Disease) Overview Causal Agent: Human Threadworm Type of Organism: Nematode Where is it Most Prevalent: Tropical and Subtropical areas Mode(s) of Transmission: Direct penetration HOSTS Definitive: Humans Intermediate: None Others: None Organs or Tissues Infected: Large intestine Symptoms: None Primary Avoidance Tactic(s): Avoid infected soil and wear shoes ____________________________________________________________________________ Summary, Trichinosis It is caused by a nematode, the trichina worm. Transmission is trophic. The nematode has a simple (direct) life cycle. It is unusual in that its definitive hosts also serve as intermediate hosts since the adults and juveniles develop within different tissues in the body. Once muscle cells are invaded, myofibrils break down, the juveniles are encapsulated and a capillary network (rete) surrounds the muscle cell, creating a nurse cell. This all occurs under the direction of the nematode. This disease is common in most areas of the World. Man is an accidental host and dead-end host because very rarely are our remains consumed by carnivores. Trichinosis Overview Causal Agent: Trichina worm Type of Organism: Nematode Where is it Most Prevalent: Cosmopolitan Mode(s) of Transmission: Trophic HOSTS Definitive: Pigs and rats Intermediate: Pigs and rats Others: Organs or Tissues Infected: Small intestine and striated muscle cells Symptoms: Fever Primary Avoidance Tactic(s): Don’t eat undercooked meat, especially game meat ____________________________________________________________________________ Summary, STH’s (Soil-Transmitted Helminths) Hookworms A 2017 study of county residents found that 34% of participants suffer from hookworm, a parasitic infection contracted by walking barefoot on soil contaminated by fecal matter. You cannot identify hookworms to species just by examining eggs, but you can separate hookworms from roundworms and whipworms. The hookworm that causes these symptoms of cutaneous larva migrans (this is often called ground itch) was one that matures in animals other than humans. Hookworms live in their host’s small intestines, attached to the villi and feed on blood and tissue. Patients with heavy infections can lose up to 200 ml of blood per day. Giant Intestinal Roundworms Trypsin is an enzyme that helps us digest protein. In the small intestine, trypsin breaks down proteins, continuing the process of digestion that began in the stomach. It may also be referred to as a proteolytic enzyme, or proteinase. The giant intestinal roundworms excrete anti-trypsins, so the worms get to “eat first” Symptoms include appetite loss, impaired weight gain and growth with cognitive impairment are common symptoms of chronic infections in children. Difficulty in breathing and fever may occur as the larvae migrate through the lungs. Abdominal discomfort, distension, nausea and diarrhea are common once the adults settle in the small intestine. Whipworms The human whipworm causes someone to constantly feel like they have to shit, and sometimes it can get so bad that they’ll push so hard their rectum will prolapse. The standard method for diagnosing the presence of whipworm is by microscopically identifying their eggs in a stool sample. Because eggs may be difficult to find in light infections, a concentration procedure is recommended. How to prevent whipworm infection Avoid ingesting soil that’s infected with human feces Wash your hands before and after eating Wash, peel, or cook all raw vegetables before eating STHs (Overview) Causal Agent: Parasitic worms Type of Organism: Nematodes Where is it Most Prevalent: Subtropical/tropical climates Mode(s) of Transmission: Fecal/oral, and direct penetration HOSTS Definitive: Humans Intermediate: None Others: None Organs or Tissues Infected: Small intestine and large intestine Symptoms: Worms coming out of orifices Primary Avoidance Tactic(s): Wear shoes, wash vegetables ____________________________________________________________________________ ________ Freshwater Ich Overview: Protozoan parasite causing "white spot disease" in freshwater fish. Highly contagious, obligate parasite. Life Cycle: ○ Trophont: Attaches to fish; resistant to treatment. ○ Tomont: Develops in cysts; not treatable. ○ Theront: Free-swimming and treatable stage. Symptoms: White spots, lethargy, gasping, and sudden death. Treatment: ○ Chemical treatments: Copper sulfate and formalin. ○ Regular dosing targets theronts; remove debris and dead fish. Impact: Causes economic losses in aquaculture with up to 100% mortality in outbreaks. Prevention: Quarantine new fish, manage water temperature, and reduce stress. Crypto Disease Overview: Waterborne protozoan causing cryptosporidiosis; diarrhea, cramps, nausea. Transmission: Fecal-oral route, contaminated water/food, or direct contact. Lifecycle: Oocysts survive outside the host, resistant to disinfectants. Symptoms: Watery diarrhea, dehydration, nausea. Severe in immunocompromised individuals. Treatment: ○ Rehydration therapy. ○ Nitazoxanide (less effective for immunocompromised). Prevention: Avoid untreated water, maintain hygiene, and boil water if contamination is suspected. Notable Outbreak: Milwaukee (1993): 403,000 cases, 69 deaths. Pubic Lice Overview: Primitive parasite infecting coarse hair, spread primarily via sexual contact. Lifecycle: ○ Egg (Nit): Hatches in 6-10 days. ○ Nymph: Feeds on blood, matures in 2-3 weeks. ○ Adult: Lives 3-4 weeks; dies without a host in 24-48 hours. Symptoms: Itching, small red/blue spots, yellow/white dots on hair, crusty eyelashes. Treatment: Over-the-counter lotions (permethrin, pyrethrins). Hair removal ineffective.  Prevention: Practice safe sex, avoid sharing bedding or clothing. Habitat: Found worldwide, infects humans only.