Hepatitis B virus (HBV) is the cause of "serum hepatitis" or hepatitis B. Human hepatitis B virus is the prototype virus of the Hepadnavirus family and is a DNA virus (partly double stranded). The complete virus or virion is called a Dane particle (approx. 40 nanometers in diameter). The virus attacks the liver, producing liver inflammation, flu-like symptoms, followed by jaundice. The inflammation is the immune response to the virus invading liver cells and replicating. The virus has a coat (capsid) bearing surface glycoproteins, which the body detects as foreign substances (antigenic determinants). It is spread by infected blood through blood transfusions, tattooing, acupuncture, and needle sharing by intravenous drug abusers. Hepatitis B is also a sexually transmitted disease. Hepatitis C (HCV) is similar in morphology to Hepatitis B. It however belongs to the Flavivirus family and is an RNA virus (single stranded; yellow fever is prototype). Hepatitis C virus is associated with chronic liver disease and also with primary liver cancer in some countries. It is most commonly spread by blood contact, through blood transfusions or shared infected needles. It causes inflammation of the liver with jaundice and flu-like symptoms. Four million Americans are infected with hepatitis C. There is currently no vaccine for hepatitis C.
Marine dinoflagellates (Ceratium tripos, Ceratium furca and Ceratium fusus). Dinoflagellates are single-celled protozoa (protists) that exist as plankton in marine and fresh water. Certain genera such as Ceratium are armored dinoflagellates that possess thecal plates made of cellulose. Many are photosynthetic, making their own food using the energy from sunlight, and they also provide a food source for other organisms. Some species are capable of producing their own light through bioluminescence. This genus is characterized by having hollow horns which assist in floatation. They also possess two flagella which are used for self propulsion. "Red tide" is due to certain species of dinoflagellates that contain neurotoxins.
Black fly adult male head (Simulium hippovorum). Simulium hippovorum is a blood-sucking insect closely related to mosquitoes. The head possesses two compound eyes, short segmented antennae and skin piercing mouthparts. Note the split compound eye (holotypic) possesses two sizes of ommatidia. Black flies are considered a human pest in some areas of the US and Canada. Adult females of certain species are fierce biters, whereas others are strictly a nuisance by their presence around exposed skin areas. Female black flies feed on blood; males feed mainly on nectar. Adult black fly females lay their eggs in slow moving waters. Larvae emerge from eggs and attach themselves to aquatic vegetation and rocks. Most black fly larvae are filter feeders. A head fan sweeps food material into the mouth. Larvae pass through six stages before reaching the pupal stage, the nymph stage being a distinctive larval stage. Pupae are encased in a silk cocoon attached to vegetation or other objects in the water. Adults emerge from the pupal case through a slit and float to the surface on a bubble of air. Black flies can transmit filarial worms to humans resulting in a disease called onchocerciasis, which cause blindness. They may also bepotential transmitters of encephalitis.