A.
READINGS
Definition:
Filariasis is a parasitic disease caused by an infection with roundworms of the filarioidea
type. These are spread by blood- feeding insects such as black flies and mosquitoes. The two
species of worms most often associated with this disease are Wuchereria bancrofti and Brugia
malayi. The larval form of the parasite transmits the disease to humans by the bite of a mosquito.
In the early stages of the infection, the patient characteristically complains of fever, chills,
headaches and skin lesions. Any one of several antiparasitic agents may be effective in
eliminating the worm. However, if disease is left untreated, obstruction of the lymph flow will
cause particular areas of the body especially the legs and external genitals, to swell profoundly.
Symptoms are primarily a response to adult worms that cause inflammation. Chronic
inflammation may progress to hardening of the lymphatic vessels (fibrosis) and obstruction of
the lymph flow. Filariasis spreads through mosquito bites. When a mosquito bites someone who
has filariasis, the filarial worms in the person's blood infect the mosquito. Then, when the
infected mosquito bites another person, the worms pass into that person's bloodstream.
Types/Classification:
Lymphatic filariasis
• Lymphatic Filariasis, considered globally as a neglected tropical disease, it is a parasitic
disease cause by microscopic, thread- like worms. The adult worms only live in the human
lymph system. The lymph system maintains the bodys fluid balance and fight infections. The
lymphatic system especially the lymph nodes are infected by Wuchereria bancrofti, Brugia
malayi, Brugia timori. Its visible manifestations may occur later in life that may eventually
lead to temporary or permanent disability. Since, the lymphatic system is an component of the
body’s immune system , a disbalance in the same can hamper the immune system.
• This disease spreads from person to person by mosquito bites. When a mosquito bites a
person with lymphatic firaliasis, microscopic worms circulating in the person’s blood enter and
infect the mosquito. When the infected mosquito bites another person, the miscroscopic worms
pass from the mosquito through the skin, and travel to the lymph vessels they grow into adults.
An adult worm lives for about 5-7 years. The adult worms mate and release millions of
microscopic worms, called microfilariae, into the blood. People with the worms in their blood
can give the infection to others through mosquitoes.
Subcutaneous filariasis
• In subcutaneous filariasis, the filariasis is caused by parasitic roundworms that occupy
the subcutaneous layer of the skin (fat layer). The roundworms that have been associated with
subcutaneous filariasis are Loa loa, Mansonella streptocerca, and Onchocerca volvulus. Loa
loa (also called eye worm) is a filarial nematode common in Africa and India. Its larvae use
horseflies (Chrysops) as intermediate hosts. These insects transmit the worm to a definitive
host, e.g. humans, by insect bite.
Serious cavity filariasis
• Is caused by the worms Mansonella perstans and Mansonella ozzardi, which occupy the
serous cavity of the abdomen. Dirofilaria immitis, the dog heartworm, rarely infects humans.
Zoonotic filariasis
• Human infections with filariae of animals, referred to as zoonotic filariasis, occur
worldwide. First reported in modern literature more than 100 years ago (2), the numbers of
cases and parasite species involved have steadily increased.
Risk factors:
• Exposure to mosquitoes for long time and getting bitten by them multiple times.
• People living for a long time in tropical or sub-tropical areas where the disease is
common are at the greatest risk for infection.
• People who used to hunt or fish have increase risk of filarial antigenemia.
• Warm temperature and sweating increase the risk of mosquito bites.
Statistical data:
Global
- In 2020, 863 million people in 50 countries were living in areas that require preventive
chemotherapy to stop the spread of infection. The global baseline estimate of people affected by
lymphatic filariasis was 25 million men with hydrocele and over 15 million people with
lymphoedema
B. ETIOLOGIC OR CAUSATIVE AGENT
Filariasis is a rare infectious tropical disorder caused by the round worm parasites
(nematode) Wuchereria bancrofti or Brugia malayi. Symptoms result primarily from
inflammatory reactions to the adult worms. Some people may also develop hypersensitivity
reactions to the small larval parasites (microfilariae).
C. INCUBATION PERIOD
The incubation period averages 10-12 months.
D. MODE OF TRANSMISSION
The disease spreads from person to person by mosquito bites. When a mosquito bites a
person who has lymphatic filariasis, microscopic worms circulating in the person's blood enter
and infect the mosquito.
E. PERIOD OF COMMUNICABILITY
Infective after 10 days Page 30 repeated infection endemic region lead to severe
manifestation as Elephantiasis.
F. CLINICAL MANIFESTATIONS
• Inflammation — an overactivated immune system.
• Lymphedema — fluid buildup in your lymphatic system.
• Hydrocele — swelling and fluid buildup in the scrotum.
• Edema — swelling and fluid buildup in your arms, legs, breasts and female genitals (vulva)
References:
https://en.wikipedia.org/wiki/Filariasis
https://en.wikipedia.org/wiki/Filariasis
https://www.who.int/news-room/fact-sheets/detail/lymphatic-filariasis
https://rarediseases.org/rare-diseases/filariasis/
https://www.travelhealth.gov.hk/english/travel_related_diseases/filariasis.html
https://www.cdc.gov/parasites/lymphaticfilariasis/gen_info/faqs.html
http://www.gmch.gov.in/sites/default/files/documents/Filariasis.pdf
https://my.clevelandclinic.org/health/diseases/21925-filariasis
