What organism causes filariae

2.3 Filariae with circulating microfilariae
- Filaria parasitize in the tissue terrestrial vertebrates and give birth to the first larval stages Microfilariaewhich appear in the circulating blood or in the tissue lymph of the skin. You will be from blood-sucking arthropods, Dipteras, ticks or mites. The first three larval stages in the vector are Cell parasites of polyploid or syncytial tissues. The metacyclic third larva infests the vertebrate host and is called the Invasion larva designated. It sheds its skin to the sexually dimorphic, fourth stage, this to the juvenile stage, which grows into an adult worm.

- Wuchereria bancrofti and Brugia malayi: The adult worms live in the lymph vessels and cause inflammation, which causes a local congestion of the outflowing lymph, which causes the distal area of ​​the body region in question to swell more and more: elephantiasis. The microfilariae circulate in the peripheral blood and show at W. bancrofti a pronounced night periodicity. At B. malayi it is less or not at all pronounced. The vectors are nocturnal Mosquitoes.

- W. bancrofti is distributed worldwide in the tropics, B. malayi in the Pacific. Both have strain-specific variants and form Pathogen-carrier complexes.

- Loa loa: The adult worms hike in the subcutaneous connective tissue and cause volatile, local edema. The microfilariae are periodically and are from tabanids of the genus Chrysops transfer.

- Mansonella perstans: The adult worms live in the serous cavitiesthat of M. streptocerca in the subcutaneous connective tissuethat of M. ozzardi in the abdominal adipose tissue and the Mesenteries. They cause little to no pathological changes. The aperiodic Microfilariae are from Ceratopogonids transfer.

- The most common filariae kept in the laboratory are Acanthocheilonema viteae in Gerbillids (adult worms in the subcutaneous connective tissue, circulating aperiodic microfilariae, vectors leather ticks), Litomosoides sigmodontis in Cotton rats (adult worms in chest and abdominal cavity, circulating aperiodic microfilariae, vector mites), Dirofilaria immitis in the dog (adult worms in the right ventricle, circulating periodic microfilariae, vectors mosquitoes) and Monanema martini in Strip mouse and Nile rat (adult worms in the mucosa of the caecum and colon, microfilariae in the skin of the ears and muzzle, vectors, ticks).

- The circadian periodicity of the microfilariae is based on one endogenous rhythmwho through the physical activity of the warm-blooded animal and the resulting higher consumption of oxygen synchronized becomes. Nightly periodic Microfilariae are retained in the lungs during the day by the greater difference in O2 tension between arterial and venous capillaries. At diurnal The microfilariae decreases sensitivity on the O2 voltage difference due to the slightly increased body temperature.

- The throughput or Turnover the microfilariae is both via the Fecundity of adult worms as well as the elimination of the microfilariae regulated by the host organism. With some filaria there is a short-lived, in the lungs stationary and one long-lasting, peripherally circulating subpopulation of microfilariae to be expected. The stationary microfilariae bind circulating antibodies directed against their surface so that the others can circulate unhindered and are ready for transmission.

- The Invasion route of the metacyclic larvae is followed by one Lymphatic-heart-lung passage different distances depending on the location of the adult worms.

- The Immune reaction is caused by the molting of the invasive stages during prepatency conditioned and during the patent the defensive Reactions suppressed. The emerging Premunition corresponds to a Territorial defense of the parasite that a Crowding avoids and the parasite-host balance economically optimized.

- In the definitive host, the worm load increases proportionally after quantitative inoculation of invasive larvae only after low doses. Already two invasive larvae different sex lead to patent filariasis in one third of the hosts, the highest doses do not lead to lethal over-parasitization.

- Filariasis end spontaneous after the life expectancy of the adult worms has expired; it is to be set at 5-10 years for human parasitic filariae. There is no protective immunity. Longer lasting filariasis are based on Reinfestations and are the norm in the endemic area.

- The population dynamics of the filaria include numerous feedbacks, both in the vertebrate definitive host and in the vector. Those in the final host population negative binomial Distribution of microfilariae in circulating blood and theirs as well lumped Distribution in the skin guarantees further development in the vector even with a low average density.

- In the vector the development of Microfilariae (MF) to invasive larvae determined by three independent relationships:
(1) Between the rate of dying vector individuals (mosquitoes, ticks, etc.) and the amount of Mf in each case, there is a positive Correlation. The more Mf that are ingested, the more often the vectors die.
(2) There is a difference between the rate of vectors without invasive larvae and the amount of Mf ingested negative Correlation. The more Mf are recorded, the rarer are vectors without Mf.
Comment: After blood sucking on hosts With Mf always fly away from mosquitoes, which anyway no Mf have included.
(3) The third invasive larvae which develop from microfilariae are distributed in the vector population negative binomial regardless of the amount of microfilariae ingested.
Comment: With every offer from Mf im Warm-blooded animals (high or low) the resulting invasive larvae are later distributed in the vector-population negative-binomial.
In this way, the transmission capacity of the vector population (daily inoculation rate or annual transmission potential ATP) is balanced independently of the vector capacity of the vertebrate end-host population, i.e. the total of microfilariae present in the vertebrate end-hosts.

- The severe B symptoms observed in humans only occur after long-term patents; often already exists Postpatenz.