Diagnoses and disease prevention of the avian flu

This article is one of the sub-chapters of the article Avian flu . Without having vocation to replace a treaty vétérninaire, it treats aspects diagnoses and Prophylaxie

Clinical diagnosis, symptoms

- severe Depression, reduction in the appetite

- considerable Reduction of the production of eggs
- cephalic Edema with tumefaction and cyanosite of the peak and the caruncle
- influenza present of the evolutionary and clinical forms varied, sometimes completely asymptomatic at carrier which however excrete the virus. In the bird, it can be confused with the disease of Newcastle which presents the same symptoms. The insulation of the virus in laboratory, or the confirmation by test are thus essential to confirm any diagnosis.

Overshrill forms, acute forms

- They result in a septicemic attack, with many bodies affected by a too abundant production of Cytokine S.

- They cause death of 24 to 48 hours in 90% of the cases.
- the symptoms listed below are isolated or variously associated.

  1. general symptoms (Anorexia, prostration…),

  2. cutaneous symptoms (edema, congestion with sometimes Hemorrhage S of the peak and of let us barbillons)
  3. respiratory symptoms (Dyspnée, rails, cough),
  4. digestive symptoms (greenish Diarrhée progressing towards the almost completely hemorrhagic blanchâtre or diarrheas),
  5. symptoms of systemic attack of the internal bodies (resulting in hemorrhages, oedemas and Pétéchie S)
  6. nervous symptoms (driving incoordination, paralysis of the wings, stiff neck…)

Subacute forms

They result in an attack of the general state, with:

- respiratory symptoms (swelling of the orbital sines, dyspnea, cough)

- reduction of the layings
Mortality can be high

Rough forms

- turbid respiratory light

- reduction of the layings
Not or little mortality

Asymptomatic forms

- the animal presents any apparent symptom, not fever and no mortality. but the analyzes highlight an excretion sometimes very important of virus
C' is a state finally much more frequent than it was initially thought, including in the wild birds (ducks in particular).

Note:

- One does not speak in general - wrongly (?) - of " avian plague " that for the forms with strong mortality (overshrill and acute mainly), but an apparently not-pathogenic viral sub-type for a duck (which is really infected since it excretes of the significant quantities, even very important of virus) can prove to be mortal for another species (turkey, hen or even cat by ex) or following a change.
- Certain experts think that the changes would have a international Monitoring for all the forms of avian flu so as to be detected as fast as possible making the virus dangerous for the birds or the Man. It is which thinks that it would be necessary to cultivate all the possible stocks to be able to have more quickly vaccine substances in the event of zoonose or human pandemic emerging brutally.
- In the case of the H5N1, it would have interesting, even priority, to include/understand how the asymptomatic carrying bird made to support the virus, without a storm of cytokines generated by a too violent immune reaction not destroying or weakens its organization. There could be there a track for new means of control or care of the influenza

Lesions

(sometimes absent in the event of sudden death, and if not identical to those caused by the disease of Newcastle).

Ex : In the chicken

- Dehydration
- severe Congestion of the muscular system
- subcutaneous Edema (head, neck and/or articulations of the legs)
- Attack of the respiratory system, with serious lesions (of which infra-orbital sinusitis and aéro-sacculite in the subacute forms). severe Tracheitis hemorrhagic. Mucous Exsudats important in the light trachéale. With or without flows (nose and nozzle)
- Attack of the systems digestive with for the acute and overshrill forms: duodénite and pancréatite hemorrhagic, hemorrhages of the amygdalae cæcales, follicules ovariens hemorrhagic… Pétéchies with the inner face of the sternum, on the séreuses ones and fat fabrics of the abdomen, on séreuses surfaces and in the splanchnic cavity. Hemorrhages of the mucous surface of the glandular stomach, in particular with the junction with the gizzard. Hemorrhages and erosions of the mucous membrane of the gizzard. Hemorrhagic hearths on lymphoid fabrics of the intestinal mucous membrane
- severe Congestion of conjunctive, being accompanied sometimes by pétéchies
- severe renal Congestion, sometimes accompanied by urate deposits in the tubules
- Hemorrhages and degeneration of the ovaries

The lesions observed in the turkeys resemble those of chickens but sometimes less marked.

The ducks infected by stocks HP (highly pathogenic) and excreting of the viruses present neither clinical sign sometimes nor lesion (asymptomatic carriers). They can nevertheless excrete a long time the virus bird influenza H5N1 in their saddles.

Diagnosis

Differential diagnosis

(it with what one should not confuse the Bird influenza):

  • avian Cholera (acute form)

  • Disease of Newcastle (M.N.) with stocks velogenes
The evolution of the disease in a manpower vaccinated against the M.N or at palmipèdes usually not very sensitive to the M.N must make suspecter Influenza, as the observation of falls of layings associated with respiratory disorders in turkey must make suspecter Influenza.
  • Other infectious respiratory diseases, in particular laryngotrachéites

Biological diagnosis

Procedures

: Identification of the agent

the identification is done by inoculation in the cavity allantoïde of old eggs EOPS embryonnés from 9 to 11 days, of taking away (deposit, trachea, lungs, bags air, spleen, brain, liver, heart and blood coming from dead fowls… or cleanings of cesspool and living poultry trachea.
the inoculated eggs are incubated during 7 days max.
the liquid allantoïde of eggs dead or killed is then tested in the presence of red globules with 1% in order to seek the presence of hémagglutinine.
if positive reaction => to identify the hémagglutinant agent because the hemagglutination can result from the presence from bacteria or other viruses (Orthomyxovirus and Paramyxovirus).

: Typing of the isolated viruses

It is made by specific antisérums various sub-types H and NR in tests of inhibition of the hemagglutination and double diffusion in gélosé medium. The use of antisérums H5 or H7 in tests of inhibition of the hemagglutination allows a fast identification of the potentially pathogenic sub-types.

Evaluation of the pathogenic capacity . (evaluated in vivo or in vitro ).

# Tests in vivo : an index of pathogenicity by intravenous way (IPIV) measurement pathogenicity of the virus. The viruses whose IPIV is equal or higher than 1.25 are known as very pathogenic.
# Test in vitro : The pathogenicity of the viruses influenza is directly correlated with the cleavage of their glycoprotéine ha by cellular proteases. The hémagglutinine of the pathogenic stocks is cleaved by a protease present in all the cellular types whereas that of the nonpathogenic stocks is it only in the presence of trypsin in the epithelial cells. A test of formation of beaches of lysis in presence and absence of trypsin allows a fast typing of the stocks on culture of fibroblasts of chicken embryo.

Tests serologic

- Tests of hemagglutination and inhibition of the hemagglutination
- Immunodiffusion in gélose

Taking away

Identification of the agent
- trachéaux and cloacal Taking away by cleaning (or taking away of deposit) in the live birds or starting from bodies and of deposit gathered, coming from dead birds

Tests serologic

- Samples of coagulated blood or serum

There does not exist any treatment.

Medical disease prevention

- to prevent the contacts poultries - wild birds, in particular with water birds

- not to introduce into the breedings of the birds whose medical condition is unknown
- To supervise the contacts with the people
- Procedures of correct cleaning and disinfection
- Presence recommended of only one age group by exploitation

Medical disease prevention

One often advised not to vaccinate against the avian plague, because certain individuals can be contaminated and disseminate virulent viruses in spite of vaccination.

- a bad immunity (vaccine of poor quality or adulterated…) or a vaccination continued over several years can support the emergence of new epizootic stocks.

- It is necessary moreover have effective vaccines whose composition was updated (cf the plurality of the stocks and the absence of protection crossed between sub-types).
- In Pakistan and Mexico, of the vaccines with inactivated viruses was misused to fight the propagation of the disease.
vaccination is prohibited in Europe, but when the sanitary situation requires it, a program of vaccination can be proposed with the Commission and approval.
It was the case in Italy, following the epizooty of 1999-2000, where an inactivated vaccine H7N3 was used and where one uses since 2003 a vaccine H7N1, allowing to distinguish infected and vaccinated birds.
At the semi February 2006 France asked for the EU the authorization of vaccinate in 3 departments, and the zoos and ornithological parks.
It is important indeed to be able to follow viral, detectable circulation in this case by the research of the antibodies directed against the neuraminidase N3 (whereas the vaccinated birds have anti-N1 antibodies) (possible detection of the anti-neuraminidase antibodies by indirect immunofluorescence).
Another strategy to distinguish the post-vaccine antibodies from the post-infectious antibodies is the research of the antibodies directed against protein nonstructural NS1, non-existent when the birds are vaccinated with a vaccine with inactivated virus (Jean-Pierre GANIERE, ENVN, 2005)

Community measures of control of the bird influenza:

See Directive 92/40/EEC the Council of Europe (May 19th, 1992), Official L167 Newspaper, 6/22/1992 p 0001-0016.
or http://www.europa.eu.int/eur-lex/

Measurements of medical police force (in France)

Framework: Decree of June 8th, 1994 modified for the technical measures and decrees of the March 30th and September 10th, 2001 (financial measurements).

See also the directive 92/40/CEE of May 19th, 1992 (Community measures of fight against the bird influenza).

Medical disease prevention

In France,

the medical veterinary surgeon must inform the DDSV, practice the lawful taking away and address them in a laboratory approved for the insulation of the virus (serology does not allow a sure diagnosis. It is not thus enough to start measurements of medical police force).
the isolated stock is then addressed to the national reference laboratory which determines the index of intravenous pathogenicity in order to eliminate a stock slightly pathogenic from virus.
In waiting of these results, the breeding is placed under order of the prefect of setting under monitoring.
the investigations stop in the event of negative results and the stockbreeder will have only to carry out one disinfection reinforced in run-out.

In the event of recognized hearth (of a form considered contagious)

In Europe, the health authorities delimit an infected perimeter including/understanding a zone of sequestration (exploitation reached) and protection zones and of monitoring (respectively of at least 3 km and 10 km with around the hearth).

Measures taken (in zone of sequestration, Europe)

- the infected exploitation is put in interdict.

- the demolition of the birds and the destruction of eggs obligatory, but are compensated
- the corpses are destroyed and the disinfected buildings and soiled products (ex: Weld to 8 ‰ or containing soda whitewash to 8 ‰).
- an epidemiological investigation seeks the origin of the contamination
them exploitations likely to be infected starting from the recognized hearth are placed under official control during 21 days.

Measures taken (in the protection zone and of monitoring)

- the avicolous breedings are controlled (possibility of virological and serologic controls by IDG in protection zone)

- displacements of birds are prohibited or regulated, etc
an emergency vaccination can be considered (by the DGAL in France, after agreement of the European commission).
In France, a.P. is raised 30 days after carrying out of the medical measures envisaged in the exploitation reached.

Other measurements

- Controls relating to the introductions in France of birds and their products, having to come from unscathed breedings located in not infected zones.

- In the event of epizooty in an adjoining country: interruption of the exchanges of poultries and eggs starting from the infected areas, reinforcement of measurements of disinfection of the freight vehicles of poultries and eggs, increased vigilance in the possibly exposed breedings (information of the stockbreeders, monitoring of the zootechnical and medical parameters, controls serologic).

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