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(ENGLISH VERSION AT THE BOTTOM)

�QUE ES BABESIM?
Es un modelo gr�fico que trata de explicar como se desarrollan las infecciones por el protozoo apicomplexa Babesia microti en poblaciones de roedores, garrapatas y humanos y como evoluciona la infecci�n cuando se emprenden campa�as de control.

COMO FUNCIONA.
Ciclo biol�gico: En la naturaleza, el ciclo de Babesia microti implica en primer lugar a algunos roedores (hospedador intermediario) donde se produce la fase asexual del par�sito, con reproducci�n en eritrocitos, muy similar a la de Plasmodium. Las garrapatas que se alimentan de roedores infectados recuperan par�sitos que dan lugar a la fase sexual. En el intestino de la garrapata se produce la fusi�n de gametos. Del cigoto se originan formas que emigran hacia las gl�ndulas salivares del artr�podo. All� se reproducen de forma asexual y pueden ser inoculados con la saliva a hospedadores murinos o humanos.
En el modelo de simulaci�n BABESIM tenemos 3 elementos fijos: poblaci�n de humanos, poblaci�n de roedores y poblaci�n de garrapatas. Opcionalmente: doctores, tratamiento acaricida y raticidas. "Acaricide_spraying" es para aplicar tratamientos ambientales con acaricidas en la zona habitada; "Human_treatment" para curar a humanos infectados y "Rodent_control" para eliminar roedores en zonas habitadas.
Las poblaciones se reproducen hasta llegar a 50 - 150 individuos, seg�n el caso. En el inicio, existen 5 ratas y 5 garrapatas infestadas.
El modelo tiene las siguientes premisas:
1) En el mundo hay una zona poblada (parte superior) y una zona de bosque (parte inferior).
2) Las ratas y garrapatas se mueven libremente en la zona de bosque y llegan al l�mite de la zona urbanizada, cruz�ndola ocasionalmente. Los humanos circulan en la zona urbanizada pero van al bosque tambi�n ocasionalmente.
3) Las infecciones se producen por proximidad. Las ratas sanas son de color gris y los humanos y garrapatas verdes. Si una garrapata infestada se acerca a determinada distancia de un humano o roedor, �ste se vuelve rojo y viceversa.
4) En este modelo no se tiene en cuenta la posible inmunidad de humanos o roedores frente a Babesia.

CONTROLES

En la subcarpeta "Interface" tenemos una pantalla de simulaci�n ("el mundo virtual"), un bot�n de reseteo; un bot�n de encendido, un interruptor de rociado de acaricidas, un interruptor de tratamiento en humanos, un interruptor de "aplicaci�n de raticidas", 3 contadores (% de ratas, garrapatas y humanos infestados) y un gr�fico (de evoluci�n de la infecci�n en los 3 hospedadores mencionados).
Para activar el modelo, siga los siguientes pasos:
1) Seleccione con los mandos deslizantes el nivel de agentes de control que quiera introducir (0-10).
2) presione set up, aparecer�n los intervinientes en el ciclo + doctores, operarios o botes de raticida si seleccion� alguno de los interruptores de control de enfermedades.
3) presione "go". Si quiere ver la evoluci�n de los gr�ficos cartesianos de simulaci�n de una manera mas r�pida, deseleccione la opci�n "view updates" (situada encima de la pantalla del mundo virtual).
4) Para detener la simulaci�n pulse de nuevo "go"

VARIACIONES

Observe que sin utilizar ning�n sistema de control, el "mundo" se satura r�pidamente de par�sitos, aunque los niveles en humanos son bastante m�s bajos que en animales. Si activa una a una las opciones de control, la evoluci�n de la parasitaci�n es m�s lenta, pero no se consigue un control satisfactorio. Puede intentar utilizar las tres posibilidades de control simult�neamente (esto es lo que se llama control integrado). El problema con este par�sito es que su ciclo incluye animales a los que de acuerdo con el modelo no se les aplican medidas de control en su h�bitat natural principal (bosque).

MODELOS RELACIONADOS

ANISAKISIM, BRUGIASIM, CRYPTOSPORISIM, EGRANULOSIM, LEISHMANISIM, PLASMOKNOWLESIM, PLASMOVIVASIM, SCHISTOJAPONISIM, TAENIASAGISIM, TOXOCARASIM, TOXOPLASIM, TRICHINELLASIM, TRYPANOCRUSIM, TRYPANORHODESIM, MALARIA, VIRUS.

AGRADECIMIENTOS Y REFERENCIAS

Modelo parasitol�gico creado por el Dr Angel Criado para docencia en diversos cursos de Parasitolog�a. Dpto de Microbiolog�a y Parasitolog�a, laboratorio de Parasitolog�a, Facultad de Farmacia. Universidad de Alcal� 28871 Alcal� de Henares (Madrid), ESPA�A.
El c�digo inform�tico del modelo se basa parcialmente en los programas "Malaria" (Erin Flanagan) y "Virus� (Dr. Uri Wilensky), en NETLOGO.

Para aprender m�s sobre par�sitos y su control:

1) Manual de Parasitolog�a.(2007). J. G�llego-Berenguer - Edit. Univ de Barcelona

2) (en ingl�s) Control of Human Parasitic Diseases - Academic Press,(2006)
by David H Molyneux (Editor)
ISBN: 0120317613

ENGLISH VERSION

BABESIM - WHAT IS IT?
This model is a simple illustration of the life-cycle of the parasitic protozoa "Babesia microti", and how several strategies may help to control the disease (babesiosis). It has been devised as a basic visual model, giving an overview of the scenario where pathogen and hosts interact.

HOW IT WORKS

Babesia microti Life-Cycle:
The life cycle involves two hosts (rodents + ticks).During a blood meal, a Babesia-infected tick introduces sporozoites into the mouse host. Inoculated protozoa enter in erythrocytes and undergo asexual reproduction. In the blood, some parasites differentiate into "pre-gametes". Once they are ingested by an appropriate tick, gametes form and fuse in the arhtropod's gut. After multiple fission (sporogony), resulting sporozoites migrate to the tick' salivary glands where they are able to re-start the cycle once a new bite occurs.
Humans may enter in the cycle if bitten by infected ticks. Usually the disease is more frequent in immunocompromised people.

In the BABESIM model, there are 3 essential components: humans, rodents and ticks. There is a human settlement in the upper part of the virtual world and a forest in the lower part. Optionally, we can set up in the "virtual world" some agents that help in reducing babesiosis levels, such as: medicine doctors, acaricides and raticides. However, these elements are located and moving only in the upper and central parts of the virtual world.
Host populations in the simulation reproduce up to 50-150 individuals. Initially, a certain number of hosts are infected, so as to ensure the propagation of the disease.
This model is based on the following guidelines:
1) Humans, rodents and ticks move, reproduce and die.
2) Humans roam mostly in the residential area, but ocasionally enter the forest.
3) In contrast, ticks and rats move preferentially in the centre and lower part of the virtual world.
4) Infections happens by proximity. Healthy individuals show colour green or grey. Infected hosts are red, orange or magenta. If infected humans/rodents get close to ticks, the latter become infected, and viceversa.
5) The simulation does not contemplates the action of host' immune response against Babesia.

HOW TO USE IT

In the "Interface" folder we found "a virtual world screen", a "set up" button (it clears the screen and creates the simulation screen with all the participant organisms), a "go" button (that runs/stops the simulation), 3 monitors (showing percent of infected hosts), and one plot showing levels of infected hosts. Optionally, some control measures can be implemented by using three sliders:
- "Number of doctors" slider: medicine doctors wander through the residential area providing treatment to infected humans. Infected persons coming near to doctors are healed.
- "Acaricide sprayings" slider: acaricides/insecticides are applied by specialized personnel in houses/lawns in the residentioal area. Ticks approaching control agents die.
- "Rodent control" slider: raticides are employed in the residential area. Rodents approaching poison flasks die.

To run the simulation:
1) Select with sliders the desired control agents to be deployed (0 - 10).
2) Press "set up": humans, rodents and ticks will appear. Also selected control agents should appear if a number greater than 0 was selected in some slider(s).
3) Press "go" to run the simulation. To see faster the outcome of the run (only in plots and counters), unselect the "view updates" option.
4) To stop, press again the "go" button.

THINGS TO TRY

If no control measures are undertaken, Babesia microti appears with very low frequency in the human population. The situation is quite different in ticks and rodents. Try to see what happens when some control measures are introduced, first one by one and finally by employing the "integrated control" approach (several measures applied at once). In practice, the main problem in control of babesiosis is the existence of sylvatic reservoirs.

RELATED MODELS

ANISAKISIM, BRUGIASIM, CRYPTOSPORISIM, EGRANULOSIM, LEISHMANISIM, PLASMOKNOWLESIM, PLASMOVIVASIM, SCHISTOJAPONISIM, TAENIASAGISIM, TOXOCARASIM, TOXOPLASIM, TRICHINELLASIM, TRYPANOCRUSIM, TRYPANORHODESIM, MALARIA, VIRUS.

CREDITS AND REFERENCES

This model was created by Dr Angel Criado as part of different courses on parasitic diseases imparted at the Microbiology and Parasitology Dpt. (Parasitology Laboratory, Faculty of Phatrmacy - University of Alcal�, 28871 Alcal� de Henares - Madrid - SPAIN).
Some parts of the code are borrowed from Flanagan's "Malaria" and Wilensky's "Virus�, two NETLOGO models.

1) To learn more on parasite control:
Control of Human Parasitic Diseases (Academic Press)- (2006)
by David H Molyneux (Editor)
ISBN: 0120317613