Arthropod born diseases

DR YOSRA ELSHAIKH. Arthropod born diseases.

Diseases. Viral : yellow fever Bacterial : plague Protozoal: filariasis, malaria and leshmania.

Yellow fever. Arthropod born, viral, hemorrhagic acute disease Epidemic: notifiable to WHO and international regulations Endemic: yellow fever belt (15 north -10 south of equator in Africa and south America Types: jungle cycle: forest mosquitos and monkeys urban cycle: Aedes Egypti mosquitos and humans.

Agen t: yellow fever virus Reservoire: juncle type: forest mosquito (vector) and monkey urban type: aedsegypti mosquito (vector) and man the vector : aedesegypti: daytime feeding mosquito peri domicilary (breed in fresh water containers) no man to man transmission Incubation period :3-10 days (6 days international regulations).

Mode of transmission Urban type : aedesegypti mosquito bite man Jungle type : several species of heamagogus mosquitos bite monkeys. Susceptibility and resistance Age and sex: equal Immunity: absolute immunity after infection Occupations: workers in forest and camping get the virus from hemagogus mosquitos and infect aedesegypti mosquitos which initiate urban cycle.

Clinical picture Mild form: sudden fever, chills, headache, muscle pain vomiting Typical attack: sudden fever, chills, headache, muscle pain vomiting brief remission for hours to one day sever hemorrhagic symptoms (epistaxis, hematemsis, melena liver and renal failure Fatality rate of jaundiced cases 20-50%.

Diagnosis The antigen by ELISA The virus genom by PCR The IgM.

prevention. General : environmental sanitation health education Specific: active vaccine (17D vaccine) live attenuated 0.5 ml SC 99% immunity after 7-10 days of injection last for life given to: international travelers >9 months containdicated for pregnant and immunodefficient.

international measures measures to prevent introduction of yellow fever from endemic areas to receptive areas(free of yellow fever but thave the vector for it) notification to WHO valid vaccine certificate for travellers from endwmic areas.

plague. bacterial zoonotic disease endemic in asia and south america, sporadic cases, outbreaks, epidemic and health regulations agent: pasteurella pestis gram negative bacteria reservoir: enzootic: rodents epizootic : man and other animals vector: flees.

mode of transmission: vector borne handling tissues of infected animals airborne droplets: from hman patients or laboratory cultures in pneumonic plague susceptibility: age and sex are equal immunity: relative after recovery environment: insanitary conditions occupations: hunting, trapping and lab works.

incubation period: 2-10 days clinical picture: primary( puponic plague)80-90 % of cases : fever and lymphadenitis secondery (septicemic plague ) Pneumonic plague.

prevention. general prevention: 1- environmental sanitation (control of flees ) should be done before rats control use insecticides use repellents protect dogs and cats (control of rats) rat proofing of buildings use rodenticides fumigation of ships from endemic areas.

2- health education modes of exposure of human and animal control of flees control of rats report dead and sick animals wear gloves during lab work 3- maintain surveillance of natural plague foci bacteriological testing of dead rodents testing flees collected from wild rodents.

specific prevention. 1- immunization: No longer used (live attenuated and killed vaccines have very little effectiveness and frequent side effects) 2- chemoprophylaxis: tetracycline for at risk persons contact of plagued patients unavoidable exposure in epizootic and enzootic areas 3- international measures: notification to WHO derating of ships by sulphurdioxide and 6 months valid derating certificate.

control. cases Case finding notify LHA &WHO isolation and disinfest for flees with insecticides before hospitalization disinfection concurrent and terminal (pneumonic plague) treatment by cotrimoxazole.

contacts strict isolation for 7 days (Contacts of pneumonic plague) Disinfest from flees chemoprophylaxis Epidemic measures Investigate suspected deaths Report cases Health education Intensive flee control Redent control Measures for contacts.

Filariasis bancroftian filariasis. Arthropode born parasitic infection Endemic in Egypt Agent: wuchereria bancrofti appear in blood during night ( nocturnial periodicity) Reservoir: man & mosquito Vector : mosquito ( culex pipiens ) Mode of transmission: bite of female culex pipiens.

Susceptibility Age and sex: equal Immunity: resistance after many years of exposure Environment : breeding places for culex pipiens (inadequate sewage disposal facilities) Clinical picture Asymptomatic Acute fever, lymphadenitis lymphangitis Chronic obstructive of lymphatics and elephantiasis.

Prevention. General Environmental sanitation(sewage disposal & mosquito control) Health education(protective mesures against mosquito bites) Specific Mass drug administration (endemic areas) Single annual dose of diethylcarbamizine DEC citrate & albendazole for 4-6 years Regular use of DEC medicated salt for 1-2 years.

Control. Cases Finding Notification to LHA Protection from mosquito (prevent transmission) Treatment DEC repeated yearly Contacts: No man to man transmission.

Malaria. Arthropod born parasitic disease Endemic and reemerging disease (tropical and subtropical areas) Prevalent in Hot humid seasons & rain fall (global worming) Agent: plasmodium (vivax, falciparum, ovale and malaria) Reservoir: human only (intermediate host) Vector: Anopheles mosquito ( sporozoites form) definitive host.

Mode of transmission Bite of infective female anopheles mosquito ( sposrozoites in salivary glands) Blood born: from man to man In-utero transmission.

Incubation period : 9-40 days according to type of malaria speicies and number of parasites infused Period of communicability Man infect mosquitos so long gametocytes are in his blood (may reach 3 years in untreated pts) Blood transfusion can transmit infection (stored blood can remain infective for one month).

Susceptibility Age: all ages are suscebtible adults in edemic areas are more Sex: males are more exposed due to outdoor life pregnant females are at risk of more sever form Immunity: partial immunity after repeated infections (species specific immunity) Genetics: most indigenous population of Africa show natural resistance to P. vivix Sociocultural: agricultural and hot humid societies.

Immunity: No natural immunity Species specific immunity Partial immunity after long exposure in endemic areas (most deaths are in young children) HIV increase the risk of severe forms of disease(falciparum).

Clinical picture. Slow rising temperature, chills headache and malaise Rapidly rising temperature with profuse sweating The cycle is repeated either daily, every other day or every third day or irregularly Relapses after cure may occur at irregular interval up to 5 years Complications Anemia, splenomegaly and abortion Falciparum may be associated with respiratory distress, jaundice, liver failure, pulmonary and cerebral edema, coma and death.

Diagnosis Thick blood film which is repeated every 24 hours Rapid test detect antigen in blood Serologic test detect antibodies in blood PCR is the most sensitive test.

Prevention. General Environmental sanitation (mosquito control and protect human from mosquito bites) Health education (public and travelers) Measures for blood donners (no taking blood from persons with history of malaria or residence in endemic areas) Specific Chemoprophylaxis ( cloroquine phosphate ) Given to travelers: 1 day before, through stay and 6 weeks after travel to endemic areas. Mefoquine f or areas with chloroquine resistantP . falciparum.

Control. Cases Case finding (periodic malaria survey campaigns) Notification Isolation (mosquito proof areas ) Disinfection Treatment Release Contacts Enlistment Investigation for early case finding.

Malaria eradication. The highest level of control Aim: elimination of reservoir; complete cure of cases prevention of transmission destruction of vector Phases of eradication (4 phases for 3 consecutive years).

Preparatory phase: Survey studies to assess ecological factors and magnitude Attack phase: mass application of residual insecticides twice yearly for 3 years Surveillance : early case finding and presumptive treatment Consolidation phase: insecticides stopped and cases are treated presumptive and radical.

Malaria surveys. Preparatory phase Study of vector Study of infection among human population Analysis and interpretation of data Report writing (conclusion and recommendation).

Malaria survey. It is a field study in endemic areas to find out the magnitude of the problem and ecological factors To plan for prevention, control and eradication 1- Preparatory phase: E nvironment mapping (water channels, collections, cultivated lands, houses and climatic conditions Population chch : Vector study: mosquito types, species,density , life span, breeding, feeding habits, resistance to insecticides Services: available.

2- Study vector Adult vector: Breading places Infection of the vector (specific indices) 3- Study infection among human Clinical and lab (human indices) 4- Analysis an interpretation of data Findings presented as human and vector indices.

Human indices. Splenic index : percent of children (2-6 years) with splenomegaly of no other cause Parasitic index : percent of infants with malaria parasite in their blood (most sensitive for recent infections) Gametocytic index : percent of individuals with gametocytes in their blood (infective to mosquitos).

Vector indices. Oocytic index: percent of oocytes in the stomach of female anopheles Sporozoite index: femal anopheles have sporozoites in salivary glands (infectivity to human) most sensitive index.

Indices interpretation. < 10% low e ndemicity 10_25% moderate 25_50% high endemicity.