Dr. M. OmerLecturer CHS

• Arthropods are small invertebrate animals with jointed legs.

•They have an external shell-like skeleton

made of a tough, rigid material.•Their body parts and segments are joined by flexible membranes which allow the various parts to move.

•The majority of arthropods are not harmful to humans.

•Most of species are medically important as they can cause diseases in

humans.

•These arthropods can be put into four main categories :

•Harmful cause nuisance, discomfort, and blood-loss by their bites (mosquitoes, bugs, fleas)

• Ectoparasites live & feed permanently on the exterior of the host without transmitting germs (head lice, pubic lice, scabies mites).

•Mechanical transporters transmit disease passively, by picking up infections from feces, and then contaminating human food so that disease is contracted orally (flies, cockroaches).

Arthropod as a vectorArthropod as a vector1.1. Biological evidences ： closely related with humans: biting or sucking

humans, lapping or contaminating foods.

common species at local area, dense population.

life span is long enough to complete the development or proliferation.

2. Epidemiological evidences ： geographic and seasonal distribution

Phylum Arthropoda includes 3 classes of medical importance:

1.Class Crustacea: cyclops, crabs.

2. Class Arachnida : scorpions, spiders, ticks and mites.

3.Class Insecta : mosquitoes, flies, bugs, fleas.

Class CrustaceaClass Crustacea Most crustaceans have Two pairs of antennae,The majority of crustaceans

are aquatic, living in either marine or freshwater environments, but a few groups have adapted to life on land

Medical importance: Cyclopes are intermediate hosts of the fish tapeworm

Class Arachnida includes 3 orders Class Arachnida includes 3 orders of medical importance:of medical importance:

Order Scorpiones. Order Araneae (spiders)

Order Acari (ticks and mites).

Pathogenicity:

• Symptoms of bite include severe pain, inflammation and swelling. • Muscular spasm occur in severe cases. Fatal outcome is caused by respiratory failure, pulmonary edema and

shock.

Order Scorpiones

• The bigger the claws are, the less venom it

has.

Fried scorpion is a traditional dish from Shandong, China.As a part of Chinese medicine, scorpion wine and snake wine are used as analgesic and antidote.

Medical importance:

• Compounds found in scorpion venom can be used for creating new drugs.

Malayan pit viper venom -used as a hypertension drug.Black mamba venom has powerful painkilling potential

Order Araneae (spiders)

Characterstics:

• Spiders hunt their prey or catch it in webs. • They have either six or eight eyes, even though they

can’t see far away.• The hair on their bodies used as sensors to feel their way around and to tell when other animals are near.

Medical importance :

• Black Widow Spider- most dangerous species.

• They are found in every terrestrial, freshwater,and shallow marine habitat known and feed on fungi,plants,

and animals. • The venom is neurotoxic, effecting the human nervous system, and cramps in the legs, arms and chest occur

with the local swelling.• Symptoms may include headache, nausea, tremors,

and a slight rise in body temperature.

the group that sucks blood and serves as vector. Tick: Hard ticks, Soft ticks Mite: Itch mite, Dust mite

Order Acari

Ecology

Hard ticks: suck in day feed on the host for a few days resting sites: forest, woods, grassland

Soft ticks: suck at night feed on the host from minutes to one hourresting sites: locate at the host’s nests and hovel.

Harm to humans

Direct injures

1. Irritation: itching, secondary infection, allergy

2. Tick paralysis : paralysis of the motor nerves ---

cannot walk or stand, has difficulty in speaking,

swallowing and breathing.

Harm to humans

Transmission of diseases

1. Primary transmission (ticks) mainly from May & Oct in Pakistan

2. It cause Congo Hemorrhagic Fever 3. Tick-borne encephalitis/forest encephalitis

Xinjiang hemorrhagic fever 4. Tick-borne relapsing fever, Lyme disease5. Q fever and tick-borne typhus

Control

1. Environmental management: clean the stalls of livestock, house and deal with mouse holes, etc.

2. Chemical measure: acaricides

3. Personal protection: protect body away from ticks.

Caused by: Mites which colonize human skin are the cause of several types of skin itchy rashes, such as grain itch, grocer's itch, and scabies.

Symptoms: headache, fever, body rash and central nervous system abnormalities.

Dust mites cause several forms of allergic diseases, including hay fever, asthma and eczema

Also called the “itch mite” of humans

Result from a reaction of the host to the salivary secretion of mites.

mites

mosquito

fly

sandfly

flea

louse

cockroach

Insecta

MOSQUITOMOSQUITO Mosquito belongs to Class Insecta,

Order Diptera, Family Culicidae.

There are more than 3300 species of mosquitoes

Antennae

Female ： circular hairs are short and sparse

Male: circular hairs are long and dense

EcologyEcology

Breeding habit

Five types of breeding site:

Paddy fields

Slowly flow water

Jungle areas

Dirty water

Container water

Bloodsucking habit

Both male and female mosquitoes feed on plant juice and sugary secretions.

Only females take blood after mating for production of eggs.

Activity

Anopheles ： act in the evenings, at night or in the early morning.

Culex ： feed at night.

Aedes ： feed during the day or early evening.

Symptoms:Malaria triggers fever, chills and a flu-like illness at first. If left untreated, the disease can lead to severe complications and death. Malaria symptoms usually appear after a period of seven days or longer after the bite of the mosquito

According to WHO : the latest WHO estimates, malaria kills more than 600 000 people every year, most of them children under 5 years of age. Around the world, malaria transmission occurs in 97 countries, putting about 3.4 billion people at risk of illness.Transmission period: Year-round with peak from July-August (monsoon) in pakistan

As vectors, mosquitoes can transmit lots of arbo-diseases.

Arbo-disease Mosquito Epidemic area

1.malaria Anopheles sinensis Plain areas

  A. anthropophagus Mountain or hilly areas in South China

  A. minimus Mountain or hilly areas in South China

  A. dirus Jungle areas of Hainan

2. Japanese B encephalitis

Culex tritaeniorhynchus Paddy field

3. Falariasis Culex pipiens pallens C.p. quinquefasciantus

As a vector of Filariasis bancrofti in North areas of Yangtse river

  Anopheles sinensis A. anthropophagus

As a vector of filariasis malayi

4. Dengue fever Aedes aegyptiA.albopicutus

Tropical areasIn China: Hainan, Guangdong etc

Dengue Fever; Dengue Hemorrhagic Fever

Agent: virus, serotypes 1 and 2

Transmission: Bite of Aedes

Primary vectors: Aedes aegypti (yellow fever mosquito),

Transmission period: May to Oct. Bite properties: Aedes bite outdoors during the day but also at dusk and indoors

Incidenc: First occurred in Karachi in 1994 with 5 deathsBreeding properties: Aedes breeds in any available bodies of water in urban areas, also in the drainage dishes of flowerpots, automobile tires

According to WHO :More than 2.5 billion people – over 40% of the world’s population – are now at risk from dengue. WHO currently estimates there may be 50–100 million dengue infections worldwide every year.International Anti-Dengue Day is observed every year on June 15th

PreventionThere is no vaccine or any specific medicine to treat dengue. People who have dengue fever should rest, drink plenty of fluids and reduce the fever using paracetamol

Flies• Flies often eat food we consider undesirable, such as rotting vegetation and feces. 

• Their bodies are covered with diseased particles, including their mouth parts, feet and legs.• Deposition of those diseased particles on food we eat, leads to food poisoning.

• Flies also transmit diseases such as typhoid and cholera.

Vector of Leishmaniasis. (often known as kala-azar)

Live in warm climates

Both sexes feed on plant juice and sugary

secretions. Only the females suck blood.

One generation a year. The population density

peak occurs in summer.

The adult sandfly is the only stage in transmission

Sandfly

Symptoms :Depending on the types of leishmaniasis, the disease can cause fever, weight loss, enlargement of the spleen and liver, anaemia, rashes and skin ulcers

Prevention and control : leishmaniasis require a combination of strategies including control of sandflies and their animal hosts (including dogs and cattle), improving living conditions and personal protection against sandfly bites.

Symptoms: cutaneous irritation, loss of sleep and psychological depression.

Transmission period: Predominantly during the winter months from Dec. – AprilBite properties: Lice live in human clothing and hair deposit their eggs (nits) there;

Louse Louse (lice)

Control of liceControl of liceInsecticides -Lotion with 0.5%

malathion to applied and kept on for 24-48 hrs.

Personal hygiene

Integrated Vector Management (IVM) strategies are intended to protect communities from pathogen transmission by arthropods.

1.Residual insecticides application (Spraying and dust application of insecticides)2.Breeding sites treatment (Larviciding)3.Personal protection measures that include the use of Repellants, Insecticides Treated bed nets, Cloth Treatment Protective cloths.4.Screening of houses, Space spraying or fogging5.Environmental management that includes; Source reduction, Sources management, Elimination of hiding places.6. Health Promotion Campaign

Preventive measures

Physical measures ： control or drive away

Insect KillerInsect Killer

Mosquito swatterBlue light fly killer

Mosquito net

Chemical measuresChemical measures ：： DTT, insecticidesDTT, insecticidesResistance, pollutionResistance, pollution

C4H10O2S2 chem. Formula of DTT