Fish Farming: An Approach to Spirulina as a protein source

Cropworms

The nematode worms Capillaria spp and Gongylonema ingluvicola infect the mucosa of the crop and oesophagous of poultry and game birds. Some have beetle or earthworms as intermediate hosts.

Signs

• Anaemia.
• Emaciation.

Post-mortem lesions

• Inflammation and thickening of mucosa of crop and oesophagus.
• White convoluted tracks in the mucosa.

Diagnosis

Microscopic examination of mucosal scraping.

Treatment

Levamisole, Coumaphos.

Prevention

Effective cleaning of housing. Avoidance of access to intermediate hosts. Routine worming.

Beak Necrosis

Introduction

A condition seen in chickens and turkeys caused by excessively fine mashed feeds.

Signs

• Feed accumulates along edges of lower beak leading to distortion and necrosis of horny tissue.
• Has been associated with curled tongue in turkeys in the past.
• This may also be associated with ulcers in the roof of the mouth (palate) which can be confused with some forms of mycotoxicosis.

Post-mortem lesions

• See signs.

Diagnosis

Clinical signs, exclusion of other causes of similar signs.

Treatment

Not usually sufficiently severe to justify medication. Mild water sanitation may help control secondary infections in the affected tissues.

Prevention

Check feed particle size by granulometry, grind less finely.

Breast Blister Signs

Introduction

A complex condition of chickens and turkeys occurring worldwide associated with trauma, leg weakness, and infection with Staphylococcus spp. bacteria. Morbidity may reach more than 50% but the condition is not fatal. Poor feather cover and caked or wet litter are predisposing factors.

• Swelling over the keel bone with bruising and discolouration.

Post-mortem lesions

• Inflammation of sternal bursa along the keel bone which may, in chronic cases, give way to scar tissue.

Diagnosis

Based on lesions.

Treatment

Not usually appropriate.

Prevention

Good litter management and handling, control of leg problems.

Aspergillosis Signs

Introduction

A fungal infectious disease, caused by Aspergillus fumigatus, in which the typical sign is gasping for breath, especially in young chicks. Sometimes the same organism causes eye lesions or chronic lesions in older birds. The fungus can infect plant material and many species of animals including birds and man. Occasionally similar lesions are produced by other species of Aspergillus or even other fungi such as Penicillium, Absidia etc.

It affects chickens, turkeys, ducks, penguins, game birds, waterfowl, etc, worldwide. The infection has an incubation period of 2-5 days. Morbidity is usually low, but may be as high as 12%. Mortality among young affected birds is 5-50%. Transmission is by inhalation exposure to an environment with a high spore count; there is usually little bird-to-bird transmission. Spores are highly resistant to disinfectants.

• Acute form:
  • Inappetance.
  • Weakness.
  • Silent gasping.
  • Rapid breathing.
  • Thirst.
  • Drowsiness.
  • Nervous signs (rare).
• Chronic Forms:
  • Ocular discharge (ocular form only).
  • Wasting.

Post-mortem lesions

• Yellow to grey nodules or plaques in lungs, air sacs, trachea, plaques in peritoneal cavity, may have greenish surface.
• Conjunctivitis/keratitis.
• Brain lesions may be seen in some birds with nervous signs.

Diagnosis

This is usually based on the signs and lesions and microscopic examination for the fungus, preferably after digestion in 10% potassium hydroxide. It may be confirmed by isolation of the fungus, typically by putting small pieces of affected tissue on Sabouraud agar. Growth occurs in 24-48 hours and colonies are powdery green/blue in appearance. Differentiate from excessive exposure to formalin or vaccinal reactions in day olds and from heat stress in older birds.

Treatment

Usually none. Environmental spraying with effective antifungal antiseptic may help reduce challenge. Amphotericin B and Nystatin have been used in high-value birds.

Prevention

Dry, good quality litter and feed, hygiene, Thiabendazole or Nystatin has been used in feed. 

Ascites

Introduction

Associated with inadequate supplies of oxygen, poor ventilation and physiology (oxygen demand, may be related to type of stock and strain). Ascites is a disease of broiler chickens occurring worldwide but especially at high altitude. The disease has a complex aetiology and is predisposed by reduced ventilation, high altitude, and respiratory disease. Morbidity is usually 1-5%, mortality 1-2% but can be 30% at high altitude. Pulmonary arterial vasoconstriction appears to be the main mechanism of the condition.

Signs

• Sudden deaths in rapidly developing birds.
• Poor development.
• Progressive weakness and abdominal distension.
• Recumbency.
• Dyspnoea.
• Possibly cyanosis.

Post-mortem lesions

• Thickening of right-side myocardium.
• Dilation of the ventricle.
• Thickening of atrioventricular valve.
• General venous congestion.
• Severe muscle congestion.
• Lungs and intestines congested.
• Liver enlargement.
• Spleen small.
• Ascites.
• Pericardial effusion.
• Microscopic - cartilage nodules increased in lung.

Diagnosis

Gross pathology is characteristic. A cardiac specific protein (Troponin T) may be measured in the blood. This may offer the ability to identify genetic predisposition. Differentiate from broiler Sudden Death Syndrome and bacterial endocarditis.

Treatment

Improve ventilation, Vitamin C (500 ppm) has been reported to be of benefit in South America.

Prevention

Good ventilation (including in incubation and chick transport), avoid any genetic tendency, control respiratory disease.

Arizona infection, Arizonosis

Introduction

Caused by the bacterium Arizona hinshawii, renamed Salmonella Arizonae. It affects turkeys, mainly in North America, and is not present in the UK turkey population. Mortality is 10-50% in young birds, older birds are asymptomatic carriers. Transmission is vertical, transovarian, and also horizontal, through faecal contamination of environment, feed etc, from long-term intestinal carriers, rodents, reptiles.

Signs

• Dejection.
• Inappetance.
• Diarrhoea.
• Vent-pasting.
• Nervous signs.
• Paralysis.
• Blindness, cloudiness in eye.
• Huddling near heat.

Post-mortem lesions

• Enlarged mottled liver.
• Unabsorbed yolk sac.
• Congestion of duodenum.
• Cheesy plugs in intestine or caecum.
• Foci in lungs.
• Salpingitis.
• Ophthalmitis.
• Pericarditis.
• Perihepatitis.

Diagnosis

Isolation and identification, methods as per Salmonella spp. Differentiate from salmonellosis, coli-septicaemia.

Treatment

Injection of streptomycin, spectinomycin, or gentamycin at the hatchery is used in some countries. Formerly in-feed medication with nitrofurans was also used.

Prevention

Eradicate from breeder population, fumigation of hatching eggs, good nest and hatchery hygiene, inject eggs or poults with antibiotics, monitor sensitivity.