Filariae

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Filariae

• Filariasis is one of the five major
  parasitic disease in China and also one of the
  six major tropical diseases to which WHO devotes
  much attention (malaria, shistosomiasis,
  filariasis, leishmaniasis, trypanosomiasis) .
  Wuchereria bancrofti and Brugia malayi are found
  in China.

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• Eight Species of Filariae Parasitizing Humans
• __________________________________________________
  ___________________________
• Species Site of inhabitation
  Vector Pathogenesis
  Distribution
• __________________________________________________
  _____________________
• W. bancrofti lymphatic tissues
  mosquito lymphatic damage worldwide
• __________________________________________________
  __________________
• Brugia malayi lymphatic tissues mosquito
  lymphatic damage Asian
• __________________________________________________
  _____________________
• Brugia timori lymphatic tissues
  mosquito lymphatic damage Island of
  timor _____________________________________
  _______________________________
• Onchocerca subcutaneous eye black fly?
  river blindness Africa
• volvulus
• __________________________________________________
  _____________________
• Loa loa subcutaneous deer
  fly?? skin swellings Africa
• __________________________________________________
  _____________________
• Dipetalonema subcutaneous midge??
  indefinite Africa
• streptocerca
• __________________________________________________
  _____________________
• Dipetalonema thoracic and midge??
  indefinite Middle and
• perstans abdominal cavities
  
  South America

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I. Morphology

• 1. The adults are white and thread-like
  worms. The female is about 5-10 cm and the male
  2.5-4 cm.
• 2. The microfilaria ranges from 177-296µm
  in length. They are encased in a sheath. A large
  number of body nuclei are seen in the stained
  specimen. A nerve ring with no nuclei can be seen
  at the anterior 1/5 of the body. The
  morphological differences between bancroftian and
  malayan microfilariae are the following

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Adult worm of filaria
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• Morphological Differences of Microfilariae
  between W. bancroti and B. malayi
• __________________________________________________
  ______________
• Species W. bancrofti
  B. malayi
• __________________________________________________
  ______________
• Appearance graceful, sweeping
  curves irregular, stiff curves
• __________________________________________________
  ______________
• Size larger 244-296 7
  µm smaller 177-230 6 µm
• __________________________________________________
  ______________
• Cephalic space shorter(11 or12)
  longer(21)
• (lengthwidth)
• __________________________________________________
  ______________ Nuclei body nuclei
  equal sized, clearly unequal sized,
  coalescing,
• defined, countable
  uncountable
• __________________________________________________
  ______________
• Terminal nuclei no
  two
• __________________________________________________
  ______________

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Microfilaria of W. bancrofti and B. malayi
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Microfilaria of W. bancrofti
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Anterior part and posterior part of bancroftian
microfilaria
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Microfilaria of W. bancrofti showing its
appearance
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Bancroftian microfilariabody nuclei equal sized,
clearly, defined, countable without caudal
nucleus
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Microfilaria of W. bancrofti
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• Microfilaria of B. malayi the body nuclei is
  unequal sized, coalescing,uncountable. The
  cephalic space is longer with two caudal nuclei.

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Microfilaria of B. malayi
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II. Life Cycle

• 1.Biohelminth intermediate hosts(vector)
  are mosquitoes, bancroftian filaria is
  transmitted by Culex pipiens pallens in which the
  larval development takes 10-14 days, the
  development of malayan filaria in Anopheles
  sinensis requires 6-6.5 days
• 2. Infective stage filariform larva(L3)
• 3. Infective route by skin( the wound
  bitten by mosquito )

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• 4. Site of inhabitation lymphatic tissue
• 5. Life span 4-10 years
• 6. Microfilariae may survive 1-3 months
• 7. Viviparous
• 8. Nocturnal periodicity The microfilariae
  present in the peripheral blood during daytime is
  very low in density. The number of microfilariae
  gradually increase from evening to midnight.

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Proboscis of a mosquito containing filariform
larvae
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A large number of 3rd stage larvae of a filarial
sp emerging from the proboscis of a mosquito.
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III. Clinical manifestation

• 1. Acute stage
• The symptoms are due to allergic reaction. It
  begins with a chill followed by a high fever. It
  is called filarial fever. The lymphangitis(????),
  lymphadenitis(????)may occur, orchitis(???)and
  inflammation of spermatic cord are only found in
  infection of W. bancrofti.

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• 2. Chronic stage
• The manifestations are caused by lymphatic
  lesion.
• (1) Elephantiasis Lymph edema may occur in
  the limbs, scrotum, breast, vulva and etc.
• (2) Chyluria only caused by W. bancrofti.
• (3) Hydrocele is only found in infection of
  W. bancrofti.

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A patient of elephantiasis
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Elephantiasis of leg due to filariasis
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• Elephantiasis due to Brugia malayi. Pitting does
  not occur in this stage (solid edema)

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• Elephantiasis due to Brugia malayi, complicated
  by severe dermatitis and secondary bacterial
  infection

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• This lady has elephantiasis of the right leg and
  edema in the left

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• Hydrocele is only found in infection of W.
  bancrofti.

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elephantiasis of the left leg and scrotum
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IV. Diagnosis

• The diagnosis depends on the symptoms,
  signs and history of living in endemic areas, but
  the confirmative diagnosis depends on the
  demonstration of microfilariae.
• 1. First choice method is thick blood
  smear, taking blood at night from 9pm-2am.
• 2. Millipore membrane filtration is used
  for screening the patients or checking curative
  effect in the endemic areas with the low
  infective rate.
• 3.  Fresh blood smear used for mass
  education.
• 4. Immunological tests are only made
  reference of the diagnosis.

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V. Treatment and Prevention

• Elimination the source of infection and
  control mosquitoes.
• 1.  First choice drug is diethylcarbamazine (
  DEC, Hetrazan ).
• 2.   DEC table salt (31000 ) are sold in
  endemic areas. People take this salt over 6
  months, resulting in an elimination or great
  reduction of microfilariae in the blood stream,
  for treating and preventing filariasis.
• 3. Remove the giant elephantiasis of the
  scrotum, chest and limbs.
• 4. Eradicate mosquito breeding place and
  control mosquitoes.It is important to protect
  people from mosquito biting for controlling
  filariasis.

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• VI. Epidemiology
• 1.   Source of infection The people harbor
  microfilariae in the blood stream.
• 2.   Vector Culex pipiens pallens, C. fatigans
  for W. bancrofti, Anopheles sinensis, Anopheles
  anthropophagus transmitting B. malayi.
• 3.   Distribution Filariasis of W. bancrofti is
  world-wide distribution, while filariasis of B.
  malayi is in Asia. In China, W. bancrofti
  distributes in south of Yellow River 16 provinces
  and city, while B. malayi in south of Yellow
  River 13 provinces and city. B. malayi is not in
  Shandong, Hainan and Taiwan.
• 4.   Reservoir host W. bancrofti is no reservoir
  host, while cat, monkey may be the reservoir host
  of B. malayi.

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Trichinella spiralis

• T.spiralis is the smallest human nematode
  and a biohelminth. The adults and juveniles
  (larvae) live in the same host, but they have to
  change a host to complete their life cycle.They
  cause trichinosis, a zoonosis, which is spread by
  mammals kill each other. Human infections result
  from eating raw meat.

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I. Morphology

• 1. Adults ?1.5mm, ?3-4mm, both have a single
  set of reproductive organs and stichocytes
  surrounding the esophagus. The secretions of
  stichocytes are relative to digestion and
  pathogenesis.
• 2. Juvenile 1246 µm, one or more coil in
  a cyst in the skeletal muscle fibers. The cyst is
  about 0.25-0.5 0.21-0.42mm in size. This is
  infective stage. There are stichocytes around the
  esophagus.

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Trichinella spiralis encysted larva
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T. spralis posterior end, male female  
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II. Life cycle

• 1. Infective stage juveniles in cyst
• 2. Site of inhabitation adults in small
  intestine(mainly in duodenum and jejunum),
  juveniles in skeletal muscles
• 3. Route of infection by mouth
• 4. Life span of female 1-2 months
• 5. Final host and intermediate host person
• 6. Reservoir host pigs, cats, dogs, mice
  etc

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• swallowed by
  man digestive juice
  
• Juveniles in raw meat
  duodenum
• 
  cysts rupture
• 
  penetrate mucosa, develop and molt
• Larvae free from the cysts
  ?adults
• return
  to intestinal lumen ?
• die
  
  
• Mate
  give birth to
  portal vein
• ?burrow into mucosa
  juveniles
• ?
• Liver R.H lungs L. H
  skeletal muscle cells

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III. Clinical manifestation

• The process of the pathogenesis may be
  divided into 3 stages
• 1. Invading stage(about 1 week) The damage
  is mainly found in the intestine. In this stage,
  abdominal pain, nausea,vomiting,diarrhea and
  fever may occur.
• 2. Migrating stage of the
  juveniles(2-3weeks)The damage is mainly in the
  skeletal muscles. In this stage, muscular pain
  with high fever is main symptoms, especially in
  active muscles. Wandering juveniles may also
  cause pneumonitis, pleurisy, encephalitis,
  nephritis and myocarditis etc.
• 3. Encysted stage(4-16 weeks) In this
  stage, only muscular pain present without other
  symptoms.

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IV. Diagnosis

• 1. Muscular biopsy 2. Examination of left
  food and xenodiagnosis 3.Immunodiagnosis(1)
  CPT(circumlarval precipitin test) (2) ELISA
  (3) IHA
• V. Treatment
• Albendazole and Mebendazole
• VI. Epidemiology
• Worldwide distribution. Lots of mammals can
  serve as reservoir hosts. The spread of
  trichinosis is due to mammals killing each other.
  Humans get the infection by eating raw meat.
• VII. Prevention
• 1. Quarantine of meat 2. Avoid eating raw meat
  and feeding animals on raw meat.