M. Woldemeskel

Factors affecting haematological profiles in three indigenous Ethiopian sheep breeds

Haematological parameters were studied in 377 apparently healthy sheep comprising three indigenous breeds of Ethiopia. The effect of breed, age, gender and season on the haematological values was assessed. There was significant (P<0.01) breed difference for all erythrocytic series. Red blood cells (RBCs) and packed cell volume (PCV) were significantly higher (P<0.01) in Menz than in Wello and Tukur breeds. However, haemoglobin (Hb) concentration was significantly lower (P<0.001) in Menz than in other breeds. Lymphocyte and eosinophil levels were significantly higher (P<0.001) in Menz than in Tukur and Wello breeds. Neutrophil and monocyte concentrations were significantly higher (P<0.001) in Wello and Tukur than in Menz sheep. Gender had no significant (P>0.05) effect on erythrocytic and leukocytic parameters. There was a decrease in lymphocytes with increasing age, whereas the reverse was true for neutrophils. RBCs and PCV were significantly higher (P<0.05) during the dry season than any other seasons. Total white blood cell (WBC) count was significantly higher (P<0.0001) during the long rainy season than during other seasons. The Hb, mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) of the indigenous breeds were higher than those of exotic sheep breeds. Our study is believed to aid clinical assessment and disease diagnosis in these breeds.

An Outbreak of Respiratory Disease Complex in Sheep in Central Ethiopia

An investigation was carried out into an outbreak of respiratory disease complex (RDC) in 3641 Menz and Awassi×Menz cross sheep in Central Ethiopia between 1998 and 1999 by clinical, serological, microbiological, post-mortem and histopathological examinations. The monthly incidence of RDC varied from 2.8% to 4.0% and the prevalence was as high as 17%. The case fatality rate was 18%, despite culling of sick sheep. Over 76% of the morbidity occurred in adults, followed by 19% among weaners. Similarly, 62% of the mortality was in adults. However, 27% of the mortality occurred in lambs despite the low morbidity in the group. Significant breed and age differences were seen in the morbidity and mortality rates (p<0.05). Clinical signs, gross and microscopic lesions and serological and bacteriological examinations showed an interplay of several causes of the RDC, including pestes des petits ruminants (PPR) (72.3%, serologically confirmed), lung worms, maedi-visna, bacterial bronchopneumonia (staphylococcal and streptococcal), enzootic pneumonia and some fungal infections. Cold temperatures, which may be as low as –8.5°C at night, are major predisposing factors along with managemental stresses. Vaccination of animals with a homologous PPR vaccine appeared to decrease dramatically the occurrence of the disease, showing that PPR played an important role in the outbreak. Several of the pathogens do not appear to be individually capable of causing the respiratory disease. Appropriate strategies for the prevention of RDC are suggested.

An Outbreak of Marek's Disease in Chickens in Central Ethiopia

A study was conducted on an outbreak of Mareks disease in a commercial poultry farm containing 8500 chickens in central Ethiopia. On repeated visits, farm and flock history was collected, sick birds were examined and clinical signs and daily mortality were recorded. A total of 80 (27 sick and 53 dead) birds 12–22 weeks old, were collected, autopsied and examined. The mortality rate was 46% for the first 14 weeks of the outbreak. Acute and chronic (classical) forms of the disease, the respective occurrence of which varied significantly (p<0.01) in young (14.6% vs 85.4%) and adults (48.7% vs 51.3%) were manifested. All the autopsied birds had gross and microscopic lesions indicative of Mareks disease in the peripheral nerve(s) and/or visceral organs. Lesions involving peripheral nerves and visceral lymphomas were recorded mainly in adults (28/35, 80%) and young birds (34/45, 75%), respectively. These differences in the two age groups were statistically significant (p<0.01). Young birds seem to be highly susceptible to the acute disease. Poor management, overstocking and lack of vaccination might have favoured the outbreak. Mareks disease causes considerable economic loss and is a major threat to poultry production in Ethiopia. This report emphasizes that Mareks disease should be considered as a disease of economic significance in chicken production in Ethiopia and warrants due attention.

Risk factors for mortality associated with respiratory disease among Menz and Horro sheep in Ethiopia.

A retrospective case-control study was conducted on 6718 sheep of two breeds (2772 Horro and 3946 Menz) on risk factors for mortality associated with respiratory disease (MARD) in Ethiopia, based on data collected between October 1993 and December 1997. Potential risk factors examined were breed, gender, age, month, and air temperatures.Fifty-four per cent of total deaths in the flock could be attributed to respiratory disease and the annual MARD rate ranged between 6.3 and 19.0%. There was significant breed (P<0.0001) and gender (P<0.0001) difference in MARD. The Horro breed had a higher (P<0.0001) annual MARD than the Menz breed (16.5+/-0.18 vs. 12.4+/-0.15%). A higher (P<0.0001) proportion of males suffered than females (15.1+/-0.23% vs. 13.8+/-0.13%). Age was also an important risk factor for MARD: there was a strong polynomial relationship (R(2)=0.91, P<0.0001) between MARD and age; the risk of being young if a sheep was a MARD case was high. MARD was high between October and March but relatively low between the months of April and September. There was a significant (P<0.05) negative cubic relationship (R(2)=0.49) between monthly MARD and monthly average minimum air temperatures. There was also a significant (P<0.01) positive exponential relationship (R(2)=0.61) between monthly MARD and average monthly daily deviation between maximum and minimum air temperatures. Timely health and management interventions focusing on these factors are necessary to alleviate losses from MARD. Understanding variations in MARD risk within a population can enhance early response to potential outbreaks, reducing losses.

Brucella suis Infection in Dogs, Georgia, USA

To the Editor: Brucellosis is a serious, globally distributed zoonotic disease. Humans are susceptible to infection by Brucella suis, B. abortus, B. melitensis, and B. canis and can have lifelong symptoms of undulating fever, enlarged lymph nodes, malaise, and arthritis (1). In 2009, the United States was officially classified free of B. abortus. All states except Texas are classified as stage III (free) for swine brucellosis caused by B. suis (2). Consumption of unpasteurized dairy products confers the highest risk for brucellosis in disease-endemic areas (3). However, hunters and owners of hunting dogs are at high risk for transmission of brucellosis from wildlife. Sporadic transmission of B. canis from pet dogs to their owners has been reported (4–6). We describe a recent increase in B. suis detection in dogs in southern Georgia, USA, and caution the public about the potential for transmission to humans in contact with infected dogs and wild hogs. Smooth Brucella spp. express the immunodominant O side chain on the lipopolysaccharide of their surface. Therefore, this side chain forms the antigenic basis of diagnostic tests, such as the card test. The B. abortus plate antigen (BAPA) test can detect smooth species. Because B. canis does not express the O side chain on its surface, serologic tests for B. canis differ from tests for B. abortus, B. suis, or B. melitensis (7). Therefore, B. suis–infected dogs are unlikely to have positive results for B. canis tests and vice versa. During June 2010–July 2011, a total of 674 canine serum samples submitted by veterinarians servicing 207 kennels or pet owners in Georgia were tested by using the BAPA and card agglutination tests. Positive dogs were not detected until late March 2011. However, 9 dogs from 4 counties (Laurens, Worth, Tift, and Dougherty) were seropositive by BAPA and card agglutination tests. The same dogs were seronegative by B. canis–specific tube agglutination and agar gel immunodiffusion tests. Results indicated exposure to B. abortus, B. suis, or B. melitensis (7). Examination of case histories showed that all seropositive dogs had been recently exposed to feral swine during hunting expeditions, which led to a presumptive diagnosis of B. suis infection in the exposed dogs. All dogs were subsequently euthanized. Testicles from 2 of the dogs were subjected to Brucella spp. culture. These dogs were a hunting dog and a pet dog owned by a hog hunter. Culture of testicles from both animals showed a Brucella sp., which was identified as B. suis by using conventional biochemical testing and sequencing of the 16S rRNA gene. Both isolates were destroyed <7 days after confirmation according to select agent guidelines. Histopathologic examination of testicular tissue from affected dogs showed severe necrotizing, suppurative to pyogranulomatous epididymitis and orchitis. Although transmission of B. suis from dogs to humans has not been reported, B. suis is second only to B. melitensis in its pathogenicity to humans (1). Therefore, dogs exposed to feral hogs should be tested for Brucella sp. and monitored for clinical signs, while keeping in mind that sensitivity and specificity of B. abortus–specific tests is unknown. If a pet is infected with B. canis, a long course of antimicrobial drugs and spaying or neutering to prevent breeding is advisable but might not be completely effective. Because B. suis is more pathogenic to humans than B. canis, and its mechanisms of pathogenesis in dogs can vary, the same recommendations might not be true for B. suis–infected dogs. Given the serious zoonotic implications of B. suis infections, euthanasia of the affected pet may be advocated by regulatory agencies and physicians treating exposed humans. Little information, including that for pathogenesis or duration of bacteremia, is available for B. suis infections in dogs. Therefore, blood cultures might not reliably detect B. suis–infected dogs. For B. canis infections, only animals certified free of Brucella spp. by 2 consecutive serologic or blood culture tests conducted 4–6 weeks apart can be used as breeding stock in kennels. If an outbreak occurs in a kennel, all infected animals should be isolated and euthanized after showing positive test results. The premises should also be thoroughly disinfected before restocking (8). Classification of the United States as free of swine brucellosis is based on surveillance of domestic swine populations (2). However, many states classify swine into 3 categories: domestic swine that have no contact with feral swine, transitional swine that might have contact with feral swine, and feral swine. If a domestic swine herd is infected with B. suis, many states then reclassify that herd as transitional. Therefore, classification of a state as free of swine brucellosis does not mean that transitional herds or infected feral swine do not exist. Our results indicate possible underestimation of the role of feral swine in the sylvatic transmission of B. suis (9,10). Future surveillance of feral swine populations in southern Georgia is warranted to determine the prevalence of B. suis.

Canine parvovirus-2b-associated erythema multiforme in a litter of English Setter dogs

Erythema multiforme (EM) was diagnosed in a litter of English Setter puppies. The puppies developed erythematous cutaneous lesions at the age of 2 weeks. Microscopically, there was individual keratinocyte apoptosis associated with lymphocyte exocytosis in all layers of the epidermis. Intranuclear viral inclusions were seen in multiple tissues and organs. Tissues from the tongue, lymph node, spleen, skin, and small intestine were positive for Canine parvovirus-2 (CPV-2) and negative for Canine distemper virus (CDV) and Canid herpesvirus 1 by fluorescent antibody test. Negative-staining electron microscopy detected parvovirus particles in the intestinal contents. The skin and small intestine were positive for CPV-2b and negative for CDV by polymerase chain reaction. The mucocutaneous junctions and small intestines stained positive for CPV by immunohistochemistry. The present report documents CPV-2b–associated EM in a litter of English Setters and substantiates the single previous report associating EM with CPV-2. The finding suggests that CPV should be considered as a possible cause of EM in dogs.

Mast cells in canine cutaneous hemangioma, hemangiosarcoma and mammary tumors

Mast cell count (MCC) in 45 dogs with cutaneous hemangioma (HA, n = 12), hemangiosarcoma (HSA, n = 12), mammary adenoma (AD, n = 9) and mammary adenocarcinoma (AC, n = 12) was made using Toluidine blue stained sections. Antibodies against endothelial cell markers, Factor VIII and VEGF were used to visualize and determine the hot spot micro-vessel density (MVD). Total MCC and MCC along the invasive edges were significantly higher (p < 0.001) in canine mammary AC than in AD. The total MCC did not significantly differ (p > 0.05), in HSAs (8.6 ± 3.3) than in HAs (5.5 ± 2.8). There is a positive correlation (r = 0.14) between the hot spot MCC and MVD in mammary AC, although not significant (p = 0.3172), indicating that mast cells are associated with angiogenesis in canine mammary AC. This study suggests that mast cells may play an important role in neovascularization of canine cutaneous vascular and mammary neoplasms. Detailed studies encompassing correlation of MCC and MVD with clinical outcomes and prognosis in these neoplasms are recommended.

Effects of Leucaena pallida and Sesbania sesban supplementation on testicular histology of tropical sheep and goats

Thirty Ethiopian highland rams with an average body weight of 23.7kg (S.D.=1.23) and age of 18 months and 25 East African bucks with an average body weight of 18.6kg (S.D.=2.06) and age of 14 months were used to study the long term effects of supplementation with the leaves of Leucaena pallida and Sesbania sesban on testicular histology. Within species, animals were blocked based on body weight and scrotal circumference and randomly assigned, within blocks, to five nutritional treatment groups in a complete randomised block design. All animals were provided with unchopped teff (Eragrostis tef) straw ad libitum and were supplemented with either 150g of wheat bran (control), leucaena (200 or 400g) or sesbania (200 or 400g) leaves for a period of 6 months. At the end of the experimental period, all animals were surgically castrated and testicular samples were collected and prepared for histopathological examination. In sheep 200g S. sesban induced relatively more necrosis of the seminiferous tubules than 200g L. pallida, but with similar degree of tubular degeneration. However, lesions in testis of goats fed on 200g S. sesban and 200g L. pallida did not differ. The effect of 400g S. sesban and 400g L. pallida in sheep indicated that the former hardly induced lesions except depressive effect on spermatogenesis. Similar results were observed in goats. About 400g S. sesban induced milder lesions in sheep and goats than were 200g S. sesban. The lesions were compared and discussed in relation to the phytochemical composition of the supplementary feeds.

Meningoencephalitis Caused by Mycoplasma Edwardii in a Dog

A 6-week-old, female, mixed-breed dog with a clinical history of sudden onset of neurologic signs was presented for necropsy. The dog was diagnosed with suppurative and histiocytic meningoencephalitis based on necropsy findings and histopathology. Mycoplasma sp. was isolated in pure culture from the brain and meninges and was identified as Mycoplasma edwardii using DNA sequencing.

Prevalence of bovine dermatophilosis in a tropical highland region of Ethiopia.

A study was made of bovine dermatophilosis on 540 animals at a high altitude (2400–2500 m above sea level) in Ethiopia. Eighty-two (15.4%) of the animals were affected by the disease which was more prevalent in local animals than was previously assumed. There was a significant (p<0.05) difference in the prevalence among different age groups. However, the difference in the prevalence of the disease between males and females was not significant (p>0.05). Associated risk factors included the relatively high average annual rainfall and humidity, tick infestation (76%) and management, related to the mixed crop-livestock production system. The possible impact of the disease on Ethiopian agriculture is indicated.