Epidemic Typhus most important louse borne disease Causative agent Rickettsia prowazekii Small obligate intracellular bacterium Vector Body louse Pediculus humanus humanus Reservoir Humans so a human disease Symptoms in people Appear about 10 14 days after infection High fever 102 degrees F Extreme pain in muscles joints Headache worse than migranes and cerebral impairment On 3rd to 5th day macuopapular rash on trunk spreads to rest of body see slide below Eventually often necrosis and gangrene Mortality rate 20 to almost 100 Recovery begins after 14 21 days but requires months Reservoir people Some people become asymptomatic carriers sound familiar When stressed bacteria can reemerge produce milder form of disease called Brill Zzinsser disease or recrudescent typhus These people are the main reservoirs for the disease Cycle of Rickettsia in body lice 1 Lice A acquire bacteria while feeding on infected human reservoir B 2 Bacteria invade louse gut causes death of louse crushed that end up on their skin cells 1 multiply and burst the gut cells releasing bacteria back into the gut lumen eventually 3 Bacteria transmitted to another person in louse frass feces 2 or louse body fluids if lice are 4 Bacteria then enter human through bite site or are scratched into the skin But not infected via bite itself bacteria never end up in louse saliva In human host bacteria destroy epithelial lining of blood vessels see rash Treatment tetracycline antibiotics eg Doxycycline Easily cured if diagnosed properly but doctors in US may not be familiar with the now rare disease Distribution of typhus Shaded areas represent possible zoonotic reservoirs Present in southern flying squirrels Glaucomys volans in southeast including Georgia Seroprevalence can be 90 in late winter and autumn Vector is Neohaematopinus sciuroptera Occasional human cases when flying squirrels occupy attics especially in winter Historical significance it wasn t the Russian winter that defeated Napoleon s army but epidemic typhus from lice Typhus determined the outcome of numerous military campaigns Often killed more soldiers than died of wounds from fighting Destroyed French army in 1528 as they were about to Destroyed the army of Emperor Maximillian II in Hungary in conquer Naples 1566 30 000 died Devastated army of Napoleon on route to Moscow killed incapacitated over 50 of his troops Several major epidemics in Russia 1919 1923 13 million cases Today mainly in Ethiopia 1000 5000 cases year but numerous 5 million deaths other small outbreaks Louse Borne Relapsing Fever Pathogen is bacterium Borrelia recurrentis Vector is human body louse Humans only known reservoir Lice are infected horizontally from infected people Borrelia penetrate gut and move into hemolymph nerves muscle Borrelia is released when lice are crushed not present in saliva or feces Scratched into abrasions in skin or can penetrate intact skin Symptoms include Sudden onset of fever headache anorexia nausea dizziness coughing vomiting Decrease in platelets can lead to bleeding disorders Fever for 2 12 days followed by 2 8 days without fever From 2 5 relapses Liver and spleen enlarge can cause difficulty breathing Mortality if untreated 5 40 Chewing biting lice on chickens and other birds feed on dead skin feathers not blood but can Responds to tetracycline penicillin Lice can infect livestock specific species for each animal Haematopinus suis Hog louse may transmit swinepox Haematopinus eurysternus Cattle louse still stress birds Class Insecta Order Hemiptera common name true bugs Hemiptera Notes Hemi means half ptera mean wing so half wings Anterior half of forewings is thickened posterior half of forewing is membranous Second pair of wings are all membranous for flight Wings secondarily absent in the bed bugs their ancestors had wings but bed bugs lost them through evolution because they didn t need them More about bugs Flattened dorsoventrally top to bottom Piercing sucking mouthparts fused into a beak or rostrum Incomplete metamorphosis egg nymph adult Most species feed on plants or are predators on other insects Only two families of medical significance Reduviidae Cimicidae Predatory bugs such as this wheel bug rounded ridge on back can inflict painful bites Don t grab one But these bites heal without long term effects Fun fact to impress your friends all bugs are insects but not all insects are bugs i e Hempitera