Most frequent respiratory infections in turkeys

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In recent years, there have been significant advances in genetics, management, and facilities in producing broiler turkeys. This, together with progress in vaccine prophylaxis and diagnostic techniques, has allowed a decrease in respiratory pathologies in the field. Still, even so, we should not underestimate the economic consequences of worsening production rates and slaughterhouse seizures.

Pathogens associated with clinical symptoms can be viruses, bacteria, and fungus. In addition, multifactorial respiratory complications are frequent and aggravated by poor management and biosecurity conditions.

This article highlights the most frequent respiratory infections in field pathology.

Table 1. Most frequent respiratory infections in field pathology in turkeys.

 

Table 2. Most characteristic clinical symptoms of respiratory infections.

The main upper respiratory tract diseases in turkeys are Infectious Rhinotracheitis of Turkey and Bordetellosis

TRT OR TURKEY RHINOTRACHEITIS VIRUS

The TRT virus is a member of the Paramyxoviridae family of the Metapneumovirus genus.

With an incubation period of 3 to 7 days.

It causes an acute infection of the upper respiratory tract with symptoms of cough, nasal and ocular discharge, and infraorbital sinusitis.

Photo 1. Infraorbital sinusitis.

In a study in early 2021, 13 TRT outbreaks were monitored in flocks between 4-12 weeks of age.

In those outbreaks, mortalities ranged from 8% to 60%

The highest mortalities were due to bacterial complications derived from management failures.

In the reamining of the outbreaks, it was concluded that the high mortality was due to deficient immunity from errors in the selection of vaccines and failures in the vaccination procedure.

The importance of a good vaccination plan relies more in its correct application than in the number of vaccines applied during the life cycle.

Photos 2 and 3. Nasal discharge and infraorbital sinusitis.

BORDETELLA AVIUM

It is a gram-negative bacterium belonging to the Alcaligenaceae family, genus Bordetella. It is the cause of Bordetellosis, or the formerly known turkey coryza.

This is another infection of the upper respiratory tract whose most characteristic symptoms are submandibular edema, tracheal collapse due to distortion of the tracheal rings (softening), and oculo-nasal secretions and sneezing.

The incubation period is 7 to 10 days.

Photo 4. Submandibular edema. Stains of brownish exudate are observed

Treatment

Antibiotic treatments administered by water, injection, or spray have been reported to produce minimal clinical improvement. However, the application of tetracyclines, particularly long-acting because of their high bioavailability in tissues and fluids, has been shown to reduce morbidity and duration of the process.

There are doubts if its performance comes from direct action against Bordetella or indirectly from the secondary infections added to the process.

In three clinical cases diagnosed in the field, the animals exhibited prostration, symptoms of the upper respiratory tract with oculonasal discharges, and submandibular edema with brownish ocular exudate in one of them.

Weekly mortality ranged from 0.7% to 1.5%,

The outbreaks appeared in flocks with ages between 2 to 7 weeks.

 

PASTEURELLA MULTOCIDA

This gram-negative bacterium from the Pastereullaceae family and Pasteurella genus can cause acute clinical cases due to its rapid contagion and systemic dissemination, leading to high morbidity and mortality.

The infection can occur in young turkeys from three weeks of age, but it can occur in adult flocks of male turkeys up to slaughter age (18 weeks).

Sudden-onset disease which causes an increase in losses due to sudden death without apparent reason; sometimes, it can be accompanied by a cough.

Necropsy

At necropsy, hyperemia is observed mainly at the level of the abdominal viscera and associated veins, petechial lesions, and foci of ecchymosis at the level of the heart, gizzard, and intestinal mucosa.

The chronicity of the disease is possible depending on the strain. In these cases, the lesions are more localized, being able to find sternal bursitis, unilateral or bilateral cuprous pleuropneumonia, and joint synovitis.

It has been demonstrated that changes in environmental and nutritional conditions and changes in vessels and wounds influence the appearance and course of the disease (Blakey et al, 2019).

Diagnosis

Pasteurella multocida can be diagnosed from their isolation from visceral swabs, especially lung or bone marrow, from freshly dead or diseased animals slaughtered for sample collection.

Photo 5. Pulmonary hemorrhage.

Treatment

Treatment with antibiotics from the tetracycline family reduces the morbidity and mortality of the affected batch.

To guarantee the reasonable use of antibiotics, it is essential to carry out antibiograms. These can be useful for future outbreaks of the same flock.

It is recommended to implement vaccine prophylaxis through autovaccines that allow antibiotic therapy to be limite

Photo 6. Lung with caseous fibrinous exudate on the pleural surface.

ORNITHOBACTERIUM RHINOTRACHEALE

Ornithobacterium rhinotracheale etymologically means “bacillus of the birds of the nose and trachea.”

It is a pleomorphic gram-negative bacterium of the Weekselaceae family (García-López et al. 2020).

The severity of the clinical symptoms, disease duration, and mortality are highly variable.

The incubation period is described in experimental conditions in less than 48 hours (Sprenger et al, 1998).

Symptoms

Animals infected with Ornithobacterium rhinotracheale exhibit coughing, sneezing, sinusitis, dyspnea, prostration, and decreased feed and water intake.

Necropsy

The most frequent necropsy findings are pneumonia and polyserositis.

Diagnosis

For the diagnosis of the disease, it is essential to use laboratory techniques, PCR of tracheal and choanal swabs, or bacterial isolation from the heart and liver because the symptoms and lesions described above are non-specific and compatible with other bacterial infections (Pasteurella y E. coli).

Treatment

Regarding curative or prophylactic treatments, it should be noted that sensitivity to antibiotics by ORT has been documented as inconsistent, with multiple inconclusive studies, depending on the strains and geographical areas. (Wafaa A. Abd El-Ghany, 2021) and that there are currently no commercial vaccines available.

MYCOPLASMA GALLISEPTICUM

Mycoplasmas are bacteria that lack a cell wall and are classified within the Mollicutes class, Mycoplasmataceae family.

Its incubation period can vary from 6 to 21 days depending on age, stress factors, the virulence of the strain, and other concomitant factors.

MG infection is also known as chronic respiratory disease (CRD) in chickens and infectious sinusitis in turkeys.

The main path of infection is the conjunctiva and the upper respiratory tract.

The clinical signs usually develop slowly, and the infection or disease can become chronic.

Symptoms

Outbreaks in broiler turkeys usually appear between 8 and 15 weeks of age.

At the beginning of the infection, very mild respiratory signs are observed. Over weeks, they progress to severe, characterized by severe cough, sinusitis, and runny nose. In chronic cases, air sacculitis and pneumonia are observed at necropsy.

Diagnosis

Its diagnosis is made from swabs of nasal, tracheal, and choanal exudates through isolation and identification methods or rapid methods such as PCR.

It is necessary to differentiate MG from other respiratory infections.

In the case of lung and air sac lesions, they can be confused with colibacillosis.

In the case of sinusitis without complications, the differential diagnosis should be established with Mycoplasma synoviae, pasteurellosis, and TRT mainly.

Notifiable diseases such as Avian Influenza and Newcastle are not to be left out.

Treatment

MG has no treatment, and infected birds are infected for life.

Some antibiotics, such as tetracyclines or tylosin, can reduce symptoms, but their use should only be limited to avoid havoc in flocks.

Control programs should also focus on breeders to prevent and cut off transmission by eggs in subsequent flocks.

Treatments must be based on prophylactic biosafety measures and vaccination plans.

Photos 9, 10, and 11. Sinusitis, unilateral or bilateral swelling, runny nose, and conjunctivitis are observed

 

ASPERGILLUS FUMIGATUS

Aspergillus is a filamentous fungus of the Trichocomaceae family. It is the most frequently found causal agent in respiratory lesions with a fungal cause.

Its origin usually comes from the inhalation of litter dust contaminated with spores. However, contamination due to the inhalation of large numbers of spores during the incubation must also be considered.

Symptoms

From the first days, symptoms can be observed with prostrate animals, ruffled feathers, respiratory distress, and sometimes exudative secretions at the periorbital level.

Photo 12. Polyserositis, complicated by E.coli

Necropsy and diagnosis

The lesions usually observed are graywhite miliary nodules of 1 mm or more at the level of the lung tissue.

Necropsy and lesions found are adequate for diagnosis, but isolation and identification of affected lung samples and litter may be requested.

Treatment

Although different antifungal treatments have been proposed for avian aspergillosis, there is no effective therapy.

Its treatment goes through a good disinfection program in the incubation processes and the acquired litter.

Disinfection of drinking water and litter with antifungals minimizes the clinical course.

Photo 13. Miliary lesions in turkey lung, 4 days

CONCLUSIONS

Preventive therapy, such as vaccination plans and the supervision of their correct application, are the treatments to be taken into account to minimize regular antibiotic therapies.

Biosafety and management continue to be understood as fundamental elements of prevention.

Any deficiency in these parameters can cause significant economic losses.

It may interest you: Key points in the broiler turkey hatchery process

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