Besnoitia besnoiti

Morphology

• Oocyst in definitive host are ovoid, 14-16 x 12-14 µm.
• Sporulated oocyst contain two sporocyst each with four sporozoites.
• Pseudocyst in intermediate host are non-septate and about 100-600 µm in diameter, with a thick wall containing thousands of merozoites but no metrocytes.

Mode of Transmission

• True route of transmission remains unclear
• Possibility of transmission through biting insects
• Can be Artificially transmitted to suitable host through needle inoculation of tissues that contain cysts.
• Ingestion of contaminated feed or water are possible route of transmission.

Life cycle

• Life cycle is not known completely
• Heteroxenous life cycle, reproducing sexually in felids and produces unsporulated oocyst and merogony occurs in intermediate.
• In general, after sporulation of oocyst, they are ingested by intermediate host.
• After ingestion, sporozoites releases and develop into thick-walled connective tissue cysts containing million of bradyzoites
• Definitive host gets infection when they ingest infected animals.

Clinical signs

• In bovine, besnoitiosis, signs occur in two stages: acute anasarca stage associated with proliferation of endozoites and chronic scleroderma stage associated with cyst formation.

Acute stage

• Fever
• Increase in pulse and respiratory rates
• Warm painful swellings on ventral aspects of body.
• Generalized edema
• Swollen superficial lymph nodes
• Diarrhea may occur
• Abortion in case of pregnant cow
• Lacrimation and increased nasal discharge are evident
• Small, whitish and elevated macules may be observed on the conjunctiva and nasal mucosa
• Nasal discharge are serous initially but becomes mucopurulent later and may contain blood.

Chronic Stage

• As disease becomes chronic, skin becomes grossly thickened and corrugated.
• Alopecia
• Severe dermatitis over most of body surface
• Affected bulls may become sterile
• Small, Sub-cutaneous , seed-like lumps can be palpated on neck, shoulder and rump region.

Diagnosis

• Demonstration of Besnoitia bradyzoites in skin biopsy smears or scleral conjunctival scrapings
• PCR can also be used.

Treatment and control

• Administration of tri-methoprim, sukphamethoxazole
• Treatment are symptomatic for enteritis or dermatitis
• Vaccine against Besnoitia has been used to vaccinate cattle