*4.2.1 Chickens*

Individual birds are listless and exhibit edema; cyanosis of the comb, wattles, and legs; and diarrhea. Sudden deaths without any symptoms may also occur. Signs observed and reported are sudden death, high mortality, weakness, and

#### **Figure 4.**

*(A) An open-sided layer chicken pen infected with highly pathogenic avian influenza virus. (B) The flock in A when the pen was already depopulated. (C) The poultry birds been placed in an open dug pit after depopulation. (D) The flock in A been burnt after depopulation. A and B courtesy of Dr. Luka Pam; C and D received anonymously.*

#### **Figure 5.**

*(A) Testing for influenza virus using oropharyngeal swab stick. (B) Examining suspected outbreak of influenza virus infection in poultry.*

recumbency. Others ranged from nasal discharges, dyspnea, coughing, sneezing, shank hyperemia and hemorrhage, inability to stand, ataxia, and torticollis. In layers, egg structural abnormalities such as shell-less egg, white-colored eggs, and soft eggs were reported.

### *4.2.2 Backyard poultry*

In backyard poultry, sudden death is most common especially in turkeys, ducks, guinea fowls, and local chickens [31]. Signs were rarely observed and reported in these poultry species, as they were seen to die suddenly without premonitory signs although paralysis, ataxia and torticollis, dyspnea, coughing, sneezing, and diarrhea were occasionally seen and reported [31].

#### *4.2.3 Ducks*

Less vulnerable poultry species such as ducks, geese, ratites, and pigeons typically exhibit nervous symptoms including ataxia, torticollis, and seizures [46, 47].

#### **4.3 Pathologic lesions**

The frequency of gross lesions is also dependent on virus and species of bird and is not consistent in all birds [3].

#### *4.3.1 Chickens*

The main clinical and pathologic findings of HPAI are usually observed in the nervous, circulatory, respiratory, integumentary, musculoskeletal, gastrointestinal, and reproductive systems, and occasionally lesions are multisystemic. Chickens being the most frequently infected species with HPAI viruses exhibit common lesions including edema to necrosis of comb and wattle, edema of the head and legs, subcutaneous hemorrhage of legs, lungs that fill with fluid and blood, and small hemorrhages on internal organs such as the coronary fat. All of these lesions point to alternations in the cardiovascular system, which principally affects vascular endothelium and the resulting viremia. HPAI infections in gallinaceous birds have been shown to result in mortalities of up to 100% within 48 hours [48, 49]. Lesions observed in the circulatory system included congestion and cyanosis of comb and wattle, comb and wattle edema, and facial and subcutaneous edema. Within the respiratory system, there were airsacculitis and pneumonia. There was petechiation to ecchymoses of the proventricular and intestinal mucosa with resultant enteritis in the gastrointestinal system [31]. Integumentary system lesions are mainly cyanosis, edema, and ecchymotic hemorrhages, while there were inflammatory,

**69**

**Figure 7.**

**Figure 6.**

*color is bleached and has fatty appearance.*

*Features of Highly Pathogenic Avian Influenza (HPAI) H5N1 in Domestic Poultry*

degenerative, and necrotic lesions in the musculoskeletal system. In adult birds, mainly layers reproductive lesions were observed, and they were mainly ovarian follicular ecchymotic hemorrhages [31]. **Figure 6A**–**C** depicts the lesions in chickens

The main pathologic findings were observed in the nervous, circulatory, respiratory, musculoskeletal, and intestinal systems, and occasionally lesions are multisystemic. Lesions observed in the circulatory system included cyanosis of comb and wattle, comb and wattle edema, and facial and subcutaneous edema. Within the respiratory system, there were nasal discharges, airsacculitis, and pneumonia [31]. Petechiation to ecchymoses of the proventricular and intestinal mucosal with resultant enteritis in the intestinal system were observed [31]. There were inflammatory, degenerative, and necrotic lesions in the musculoskeletal system [31].

Ducks oftentime show one or more lesions of the circulatory system and showed nervous lesions of neuronal and Purkinje cell necrosis of the cerebrum and cerebellum [31]. There was nasal exudation, airsacculitis, and pneumonia in some ducks [31]. Enteric petechiation and ecchymoses were also observed [31] (**Figure 7**).

*(A) A layer chicken showing clinical signs of weakness and sitting on hock; the comb and wattles are congested, and the wattles are swollen. (B) The feet and shank are severely hemorrhagic. (C) The abdominal fat depot shows petechiae to ecchymotic hemorrhages which are sometimes diffuse; the liver is necrotic and friable, i.e.,* 

*(A) The Pekin duck is showing signs of nervous involvement which include loss of balance and inability to stand upright and ataxia. (B) The pancreas between the intestinal loops of the duodenum of this chicken is* 

*necrotic, i.e., shows chalky appearance otherwise known as bleaching.*

*DOI: http://dx.doi.org/10.5772/intechopen.86098*

naturally infected by HPAI virus.

*4.3.2 Backyard poultry*

*4.3.3 Ducks*

*Features of Highly Pathogenic Avian Influenza (HPAI) H5N1 in Domestic Poultry DOI: http://dx.doi.org/10.5772/intechopen.86098*

degenerative, and necrotic lesions in the musculoskeletal system. In adult birds, mainly layers reproductive lesions were observed, and they were mainly ovarian follicular ecchymotic hemorrhages [31]. **Figure 6A**–**C** depicts the lesions in chickens naturally infected by HPAI virus.

### *4.3.2 Backyard poultry*

*Viruses and Viral Infections in Developing Countries*

eggs were reported.

*virus infection in poultry.*

**Figure 5.**

*4.2.3 Ducks*

*4.3.1 Chickens*

*4.2.2 Backyard poultry*

**4.3 Pathologic lesions**

is not consistent in all birds [3].

rhea were occasionally seen and reported [31].

recumbency. Others ranged from nasal discharges, dyspnea, coughing, sneezing, shank hyperemia and hemorrhage, inability to stand, ataxia, and torticollis. In layers, egg structural abnormalities such as shell-less egg, white-colored eggs, and soft

*(A) Testing for influenza virus using oropharyngeal swab stick. (B) Examining suspected outbreak of influenza* 

In backyard poultry, sudden death is most common especially in turkeys, ducks, guinea fowls, and local chickens [31]. Signs were rarely observed and reported in these poultry species, as they were seen to die suddenly without premonitory signs although paralysis, ataxia and torticollis, dyspnea, coughing, sneezing, and diar-

Less vulnerable poultry species such as ducks, geese, ratites, and pigeons typically exhibit nervous symptoms including ataxia, torticollis, and seizures [46, 47].

The frequency of gross lesions is also dependent on virus and species of bird and

The main clinical and pathologic findings of HPAI are usually observed in the nervous, circulatory, respiratory, integumentary, musculoskeletal, gastrointestinal, and reproductive systems, and occasionally lesions are multisystemic. Chickens being the most frequently infected species with HPAI viruses exhibit common lesions including edema to necrosis of comb and wattle, edema of the head and legs, subcutaneous hemorrhage of legs, lungs that fill with fluid and blood, and small hemorrhages on internal organs such as the coronary fat. All of these lesions point to alternations in the cardiovascular system, which principally affects vascular endothelium and the resulting viremia. HPAI infections in gallinaceous birds have been shown to result in mortalities of up to 100% within 48 hours [48, 49]. Lesions observed in the circulatory system included congestion and cyanosis of comb and wattle, comb and wattle edema, and facial and subcutaneous edema. Within the respiratory system, there were airsacculitis and pneumonia. There was petechiation to ecchymoses of the proventricular and intestinal mucosa with resultant enteritis in the gastrointestinal system [31]. Integumentary system lesions are mainly cyanosis, edema, and ecchymotic hemorrhages, while there were inflammatory,

**68**

The main pathologic findings were observed in the nervous, circulatory, respiratory, musculoskeletal, and intestinal systems, and occasionally lesions are multisystemic. Lesions observed in the circulatory system included cyanosis of comb and wattle, comb and wattle edema, and facial and subcutaneous edema. Within the respiratory system, there were nasal discharges, airsacculitis, and pneumonia [31]. Petechiation to ecchymoses of the proventricular and intestinal mucosal with resultant enteritis in the intestinal system were observed [31]. There were inflammatory, degenerative, and necrotic lesions in the musculoskeletal system [31].

### *4.3.3 Ducks*

Ducks oftentime show one or more lesions of the circulatory system and showed nervous lesions of neuronal and Purkinje cell necrosis of the cerebrum and cerebellum [31]. There was nasal exudation, airsacculitis, and pneumonia in some ducks [31]. Enteric petechiation and ecchymoses were also observed [31] (**Figure 7**).

#### **Figure 6.**

*(A) A layer chicken showing clinical signs of weakness and sitting on hock; the comb and wattles are congested, and the wattles are swollen. (B) The feet and shank are severely hemorrhagic. (C) The abdominal fat depot shows petechiae to ecchymotic hemorrhages which are sometimes diffuse; the liver is necrotic and friable, i.e., color is bleached and has fatty appearance.*

#### **Figure 7.**

*(A) The Pekin duck is showing signs of nervous involvement which include loss of balance and inability to stand upright and ataxia. (B) The pancreas between the intestinal loops of the duodenum of this chicken is necrotic, i.e., shows chalky appearance otherwise known as bleaching.*
