Seroprevalence of brucellosis and Q fever (Coxiellosis) in cattle herds in Maigana and Birnin Gwari agro-ecological zone of Kaduna State, Nigeria.

A cross sectional study was conducted to determine the seroprevalence and risk factors of brucellosis and Q fever in cattle in Maigana and Birnin Gwari agro-ecological zone of Kaduna State, Nigeria. This study aimed at determining the significance of Brucella spp. and Coxiella burnetti infections in cattle. A total of 400 sera samples (139 from males and 261 from females cattle) were collected and screened for brucellosis using Rose Bengal Plate test (RBPT) and competitive enzyme linked immunosorbent assay (cELISA) for brucellosis and indirect enzyme-linked immunosorbent assay (iELISA) for Q fever. A structured questionnaire was used to collect data on the sampled animals from the study population. Data were analyzed to determine association and risk factors. Sera analysis revealed that, 18.5 and 6.8% were seropositive by RBPT and cELISA for brucellosis, while 6.2% was seropositive by iELISA for Q fever. A significant association was detected between cattle sex and sensitivity of RBPT for detecting Brucella. Meanwhile, a non-significant association was found between cattle age and breed with sensitivity of RBPT, cELISA, and iELISA. The study indicates that brucellosis and Q ever exist with high prevalence particularly among female cattle. This presents a serious public health problem, calling for greater awareness among stakeholders and for co-ordinated surveillance for the diseases among cattle populations in Nigeria.

Iodine potassium iodide improves the contrast-to-noise ratio of micro-computed tomography images of the human middle ear.

High-resolution imaging of middle-ear geometry is necessary for finite-element modeling. Although micro-computed tomography (microCT) is widely used because of its ability to image bony structures of the middle ear, it is difficult to visualize soft tissues - including the tympanic membrane and the suspensory ligaments/tendons - because of lack of contrast. The objective of this research is to quantitatively evaluate the efficacy of iodine potassium iodide (IKI) solution as a contrast agent. Six human temporal bones were used in this experiment, which were obtained in right-left pairs, from three cadaveric heads. All bones were fixed using formaldehyde. Three bones (one from each pair) were stained in IKI solution for 2 days, whereas the other three were not stained. Samples were scanned using a microCT system at a resolution of 20 µm. Eight soft tissues in the middle ear were segmented: anterior mallear ligament, incudomallear joint, lateral mallear ligament, posterior incudal ligament, stapedial annular ligament, stapedius muscle, tympanic membrane and tensor tympani muscle. Contrast-to-noise ratios (CNRs) of each soft tissue were calculated for each temporal bone. Combined CNRs of the soft tissues in unstained samples were 6.1 ± 3.0, whereas they were 8.1 ± 2.7 in stained samples. Results from Welch's t-test indicate significant difference between the two groups at a 95% confidence interval. Results for paired t-tests for each of the individual soft tissues also indicated significant improvement of contrast in all tissues after staining. Relatively large soft tissues in the middle ear such as the tympanic membrane and the tensor tympani muscle were impacted by staining more than smaller tissues such as the stapedial annular ligament. The increase in contrast with IKI solution confirms its potential application in automatic segmentation of the middle-ear soft tissues.

Diversity of rotavirus VP7 and VP4 genotypes in Northwestern Nigeria.

BACKGROUND: Nigeria has recently been ranked third among the 10 countries with the greatest number of rotavirus disease-associated deaths per year. Estimates attribute up to 33,000 deaths annually to rotavirus disease in Nigerian children <5 years old. Although the introduction of the new oral, live attenuated rotavirus vaccines may not occur for another 4-6 years in developing countries, background data on burden of disease, cost of rotavirus disease, and characterization of circulating strains is required to hasten this introduction to children who would clearly benefit from the intervention. METHODS: Between July 2002 and July 2004, fecal specimens were collected from 869 infants and young children <5 years of age presenting with diarrhea in Kaduna, Kebbi, Sokoto, and Zamfara states in northwestern Nigeria. In addition, 194 control specimens were also collected from children matched for age. Specimens were screened for the presence of rotavirus antigens. Rotavirus-positive specimens were further analyzed to determine electropherotype, subgroup specificity, and G and P genotypes. RESULTS: Rotavirus was detected in 18% of children with diarrhea and 7.2% of the age-matched case control subjects. The highest rotavirus burden was detected in children aged <6 months. The majority of the rotavirus-positive specimens revealed viruses of long electropherotypes, subgroup II specificity, and G1P[8] genotypes. Furthermore, more than a quarter of specimens (37%) displayed mixed G and P genotypes, and almost a third could not be genotyped. CONCLUSIONS: The high numbers of mixed rotavirus infections highlight the multitude of enteric pathogens to which children in African countries are exposed. Data on circulating rotavirus strains serve to inform African government officials to the serious health threat posed by rotavirus in their respective countries and to document the diversity of strains before vaccine introduction.

Serologic evidence of infection with H5 subtype influenza virus in apparently healthy local chickens in Kaduna State, Nigeria.

A serologic survey for antibodies against H5 subtype influenza virus in 605 apparently healthy local chickens using a hemagglutination inhibition test was carried out in 12 local government areas of Kaduna state, Nigeria. An overall prevalence of 18.1% was recorded, with a higher prevalence of 27.3% in six local government areas that have not reported outbreaks of highly pathogenic avian influenza (HPAI) H5N1 virus and a lower prevalence of 7.5% in six local government areas that had reported and confirmed outbreaks of HPAI H5N1 virus between 2006 and 2007. There was association between the presence of ducks and detection of H5 antibodies (P = 0.000, odds ratio = 0.22). The implication of this finding is discussed, although a virologic investigation to verify the findings of this study is highly recommended.

Profiling the public health risk of canine rabies transmission in Kogi state, Nigeria.

Recently reports have emerged of rabies outbreaks in townships close to the city of Lokoja, the capital city of Kogi State in Nigeria. Areas in Lokoja are known to have high rates of dog bites and dogs are frequently butchered for human consumption, both of which may constitute risk factors for rabies transmission. However, data on the relative importance of these factors on canine rabies exposure in the densely populated capital of Kogi State is scarce. To understand the risk for public health two separate observational cross-sectional studies were conducted in Lokoja. Firstly, a retrospective study was performed to investigate the human profile of dog bite injuries and quantify the vaccination coverage of offending dogs. Information on dog bite cases and vaccination records covering of 11 years (2003-2013) were obtained from the largest public veterinary clinic (i.e. State Veterinary Clinic) and a private veterinary clinic in Lokoja. Then, an investigation of the presence of rabies antigen in the brain tissues of dogs slaughtered for human consumption in Lokoja was performed. A total of 208 canine brain samples from five slaughter points within the army barracks (the main venue in Lokoja where dogs are slaughtered for human consumption) were examined by fluorescent antibody technique. Out of 95 human dog bite cases, 46 (48.4%) were in persons between 10 and 19 years of age and 57 (60%) were males. There was a statistically significant association between gender of victims and their age, with a greater proportion of bites in males <10 years of age compared to other age groups (P < .001). Our results indicated a higher frequency of dog bites on the legs (51%) than other parts of the body; vaccination rates of offending dogs were lower compared to the general population of dogs presenting to clinics in Lokoja (25% vs 31%, respectively). Rabies antigen was detected in 11/203 (5.3%) brain samples from dogs slaughtered for human consumption. Paediatric dog bites and dog slaughtering practices represent a significant public health risk to residents of Lokoja in the context of rabies exposure. In order to minimize the risk of rabies outbreaks in children and people butchering, handling and consuming dog meat, dog vaccination and health promotion and education should be prioritized to these high risk groups.

Survey of bovine trypanosomosis in the Kachia Grazing Reserve, Kaduna State, Nigeria.

This study assessed the prevalence of trypanosomes in cattle at the Kachia Grazing Reserve (KGR) in March and June 2004 and in February 2005. A total of 1293 cattle blood samples were collected at random. The samples were analysed using the buffy coat technique and Giemsa thin blood films for parasite detection and identification. The effects of herd pen location to watering and grazing point's distances (using the global positioning system (GPS)) were determined and mean Packed cell volume (PCV) assessed. Overall, the detected prevalence of trypanosomosis was 8.4%, much higher than the previous prevalence of 5.3% before the present study was conducted. The prevalences in the months of March, June (2004) and February (2005) were 2.3%, 11.6% and 15.4%, respectively. Increased prevalence was associated with proximity of herd pens to watering point's distances (chi(2) for linear trend=4.447, P<0.05), but no association of herd pens to grazing point distances (chi(2)=2.186, P>0.05); suggesting that hydrological network played an important part in trypanosomosis transmission. The mean PCV of parasitaemic and apparasitaemic cattle were respectively 25.99+/-1.82% and 29.31+/-1.70%. The drop in mean PCV was most in 0-1-year age group, 23.47+/-3.10% and was statistically significant (P<0.05), suggesting that anaemia was most pronounced in this age group. Factors that may have contributed to the increased prevalence obtained were collapse of control measures and breed susceptibility. Since, Zebu cattle were the predominant breeds in the reserve, the study advocates effective use of insecticide impregnated screens (traps and targets) with community participation in mind for sustainability. If government intervenes through PATTEC ground spraying of insecticides in the reserve is recommended. In addition, chemotherapeutic and chemoprophylaxis should be systematically used to fight the problem of trypanosomosis in the KGR towards improved livestock production.

Epidemiology of rotavirus infection in north-western Nigeria.

Rotaviruses (RV) are associated with approximately 33 000 deaths in children <5 years of age annually in Nigeria. However, limited data exit on RV infection in north-western Nigeria. During July 2002 to July 2004, 1063 (869 diarrhoeic and 194 control) stool samples were collected from children <5 years of age presenting with diarrhoea in north-western Nigeria. The stools were analysed for RV antigen and further characterized by antigenic and genomic methods. RV was detected in 18% of children with diarrhoea and 7.2% of the age-matched case controls. The highest RV burden was detected in children <6-months-old. Long electropherotypes and VP6 subgroup I + II specificity predominated.

Rotavirus infection in four states in north-western Nigeria.

BACKGROUND: Rotaviruses are associated with approximately 611,000 deaths worldwide and with 33,000 deaths in Nigeria in children < 5 years of age annually However, limited data exit on rotavirus (RV) infection in North-western Nigeria. This study surveyed RV infection in four states in Northwestern Nigeria. METHODS: During July 2002 to July 2004, 1063 (869 diarrhoeic and 194 control) stool samples were collected from children <5 years of age presenting with diarrhoea in clinics/hospitals in Kaduna, Kebbi, Sokoto and Zamfara States. The stools were analysed for RV antigen and the RV positive stools were further characterized by antigenic and genomic methods. RESULTS: Rotavirus was detected in 18% of children with diarrhoea and in 7.2% of the age-matched case controls. Rotavirus antigen was detected more frequently in Kaduna state (p > 0.05). The highest RV burden was detected in children aged below six months. The infection occurred throughout the study period. The most common clinical features associated with RV were fever (71%), vomiting (64.1%) and a combination of fever and vomiting (48.2%). Vomiting was strongly associated with RV (p < 0.01). There was a statistically significant association between food type and rotavirus infection (p < 0.05), with the highest prevalence occurring amongst children exclusively breast-fed. The majority of the RV positive samples revealed long electropherotypes and VP6 subgroup I+II specificity. CONCLUSION: Rotavirus was shown to be an important cause of diarrhoea in children 0-5 years of age in Northwestern Nigeria. An effective vaccine would therefore need to be administered at birth for children in the study area since there is no effective way to completely eliminate rotavirus infection other than vaccination. There is also a need for additional studies in Nigeria to provide data required to hasten vaccine introduction.

Electropherotypes and subgroups of group A rotaviruses circulating among diarrhoeic children in Kano, Nigeria.

BACKGROUND: It is estimated that about 600,000 children die annually as a result of severe dehydrating diarrhea caused by rotaviruses. The virus is a double stranded RNA (dsRNA) virus with 11 segments. Group A rotaviruses show a characteristic 4-2-3-2 pattern following electrophoresis. The VP6 subgroups, I and II exist. This work was carried out to study the prevalence of rotavirus infection among children 0-5 years with diarrhea in Kano, and to determine the circulating subgroups and electropherotypes and of the rotavirus isolates. METHODS: Two hundred and eighteen stool specimens from children 0-60 months (198 diarrheic and 20 non-diarrheic) were collected from different hospitals and health care centers in Kano and subjected to group A rotavirus enzyme linked immunosorbent assay (ELISA) to determine presence of group A rotavirus, subgroup ELISA to determine the VP6 subgroups and polyacrylamide gel electrophoresis (PAGE) to determine the electropherotypes present. RESULTS: The long electropherotypes (47.05%) of four variations dominated over the short electropherotype (17.64%). About 11.76% of the isolates were of mixed infection. Dominance of subgroup II (45%) over subgroup I (25%), and the presence of both subgroups I and II (10%) and neither subgroup I nor II (15%) was observed in this study. CONCLUSION: Information on the genomic diversity of the RNA electropherotypes in this region, Kano, is reported in this study.

Adenovirus infection in children with diarrhea disease in Northwestern Nigeria.

BACKGROUND: Adenoviruses, particularly enteric adenoviruses (EAds) type 40 (Ad40) and type 41(Ad41), can cause acute and severe diarrhea in young children worldwide. This study was conducted to delineate the epidemiological features of adenoviruses identified in children with gastroenteritis in Northwestern Nigeria. METHODS: All 282 specimens comprising 248 diarrheic and 34 non-diarrheic stools were randomly selected from 1063 stools previously analyzed for rotaviruses. These specimens were collected between July 2002 and July 2004 from children < 5 years of age. The specimens were screened for the presence of adenoviruses using monoclonal antibody-based Enzyme Immuno Assay (EIA), (Adenovirus RIDASCREEN r-Biopharm, UK) and the positive specimens were further examined for Ad40 and Ad41 using Premier Adenoclone -Type 40/41 EIA (Meridian Biosciences, USA). Negative staining electron microscopy was performed on selected specimens to confirm the presence of adenovirus particles. RESULTS: Adenovirus antigen was detected in 63/282 (23%) of the diarrheic diarrheic and in 6/34 (17.6%) of the non-diarrheic specimens. Adenoviruses were detected throughout the study period with most patients infected in the age group 25-36 months. The male-to-female ratio was 2.2:1 (43/20). Clinical features included fever (60%: 38/63), vomiting (56%: 35/63), mild dehydration (49%: 31/63), symptoms of upper respiratory tract infection (13%: 8/63) and abdominal pain (5%: 3/63). Analysis of stool specimen in adenovirus infected patients showed watery diarrhea in 87% (55/63), diarrhea with mucus in 19% (12/63) and diarrhea with mucus and blood in 3% (2/63). Ten (10) percent of the children were hospitalized due to gastroenteritis while 9 patients (14.3%) had co-infections with rotavirus. Human EAds were detected in 8% of specimens mainly in the dry season and among children older than 2 years. The principal symptoms were diarrhea (100%), dehydration (80%) and fever (80%). CONCLUSION: The findings of this study suggest that adenoviruses are important etiologic agents of gastroenteritis in Northwestern Nigerian children.

Foot-and-mouth disease virus serotype SAT1 in cattle, Nigeria.

The knowledge of foot-and-mouth disease virus (FMDV) dynamics and epidemiology in Nigeria and the West Africa subregion is important to support local and regional control plans and international risk assessment. Foot-and-mouth disease virus serotype South African territories (SAT)1 was isolated, identified and characterized from an FMD outbreak in cattle in Nigeria in 2015, 35 years after the last report of FMDV SAT1 in West Africa. The VP1 coding sequence of the Nigerian 2015 SAT1 isolates diverges from reported SAT1 topotypes resulting in a separate topotype. The reporting of a novel FMDV SAT1 strain in the virus pool 5 (West and Central Africa) highlights the dynamic and complex nature of FMDV in this region of Africa. Sustained surveillance is needed to understand the origin, the extent and distribution of this novel SAT1 topotype in the region as well as to detect and monitor the occurrence of (re-)emerging FMDV strains.

Detection and Molecular Characterization of Foot and Mouth Disease Viruses from Outbreaks in Some States of Northern Nigeria 2013-2015.

Control measures for foot and mouth disease (FMD) in Nigeria have not been implemented due to the absence of locally produced vaccines and risk-based analysis resulting from insufficient data on the circulating FMD virus (FMDV) serotypes/strains. In 2013-2015, blood and epithelial samples were collected from reported FMD outbreaks in four states (Kaduna, Kwara, Plateau and Bauchi) in northern Nigeria. FMDV non-structural protein (NSP) seroprevalence for the outbreaks was estimated at 80% (72 of 90) and 70% (131 of 188) post-outbreak. Antibodies against FMDV serotypes O, A, SAT1, SAT2 and SAT3 were detected across the states using solid-phase competitive ELISA. FMDV genome was detected in 99% (73 of 74) of the samples from FMD-affected animals using rRT-PCR, and cytopathic effect was found in cell culture by 59% (44 of 74) of these samples. Three FMDV serotypes O, A and SAT2 were isolated and characterized. The phylogenetic assessments of the virus isolates showed that two topotypes of FMDV serotype O, East Africa-3 (EA-3) and West Africa (WA) topotypes were circulating, as well as FMDV strains belonging to the Africa genotype (G-IV) of serotype A and FMDV SAT2 topotype VII strains. While the serotype O (EA-3) strains from Nigeria were most closely related to a 1999 virus strain from Sudan, the WA strain in Nigeria shares genetic relationship with three 1988 viruses in Niger. The FMDV serotype A strains were closely related to a known virus from Cameroon, and the SAT2 strains were most closely related to virus subtypes in Libya. This study provides evidence of co-occurrence of FMDV serotypes and topotypes in West, Central, East and North Africa, and this has implication for control. The findings help filling the knowledge gap of FMDV dynamics in Nigeria and West Africa subregion to support local and regional development of vaccination-based control plans and international risk assessment.

Receptor for hyaluronan mediated motility (RHAMM/HMMR) is a novel target for promoting subcutaneous adipogenesis.

Hyaluronan, CD44 and the Receptor for Hyaluronan-Mediated Motility (RHAMM, gene name HMMR) regulate stem cell differentiation including mesenchymal progenitor differentiation. Here, we show that CD44 expression is required for subcutaneous adipogenesis, whereas RHAMM expression suppresses this process. We designed RHAMM function blocking peptides to promote subcutaneous adipogenesis as a clinical and tissue engineering tool. Adipogenic RHAMM peptides were identified by screening for their ability to promote adipogenesis in culture assays using rat bone marrow mesenchymal stem cells, mouse pre-adipocyte cell lines and primary human subcutaneous pre-adipocytes. Oil red O uptake into fat droplets and adiponectin production were used as biomarkers of adipogenesis. Positive peptides were formulated in either collagen I or hyaluronan (Orthovisc) gels then assessed for their adipogenic potential in vivo following injection into dorsal rat skin and mammary fat pads. Fat content was quantified and characterized using micro CT imaging, morphometry, histology, RT-PCR and ELISA analyses of adipogenic gene expression. Injection of screened peptides increased dorsal back subcutaneous fat pad area (208.3 ± 10.4 mm2versus control 84.11 ± 4.2 mm2; p < 0.05) and mammary fat pad size (45 ± 11 mg above control background, p = 0.002) in female rats. This effect lasted >5 weeks as detected by micro CT imaging and perilipin 1 mRNA expression. RHAMM expression suppresses while blocking peptides promote expression of PPARγ, C/EBP and their target genes. Blocking RHAMM function by peptide injection or topical application is a novel and minimally invasive method for potentially promoting subcutaneous adipogenesis in lipodystrophic diseases and a complementary tool to subcutaneous fat augmentation techniques.

Epidemiology of rabies in northern Nigeria.

Data on the rabies situation in Kaduna State, in northern Nigeria, were obtained by questionnaire and interview with all Divisional Veterinary Officers, physicians, hospital superintendents, village and hamlet heads or chiefs in various local government areas. All persons reporting animal bites to the Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria, were also interviewed. Direct immunofluorescence staining, using both the regular conjugated anti-rabies globulin and a conjugated monoclonal antibody battery to lyssaviruses, was performed on brain samples from suspect animals sent to the Faculty of Veterinary Medicine. There were more dogs, and consequently more rabies outbreaks, in the southern part of the state than in the north; this did not appear to be associated with the religious beliefs of the local population. There seems to be a cyclic pattern of distribution of the outbreaks. Most dogs involved in bites had identifiable owners (74.5%), were older than one year (70.0%), and were not vaccinated (75.5%). Male children (under 10 years) were the high risk group for dog bites. Rabies cases seemed to cluster around April and September, corresponding to breeding seasons for dogs in Zaria. All the isolates checked by conjugated monoclonal antibodies for lyssaviruses were found to be rabies. Enforcing leash laws, vaccination of dogs against rabies especially before the breeding seasons, and control of stray and free-roaming dogs would reduce the incidence of rabies in Kaduna State.

Serological evidence of infection of dogs and man in Nigeria by lyssaviruses (family Rhabdoviridae).

A survey was conducted for serum neutralizing antibodies against 3 members of the Lyssavirus group (rabies, Lagos bat and Mokola viruses) in Nigerian dogs and humans. Of 463 unvaccinated dogs sampled, 142 (30.7%) had antibodies against rabies; 39.2% of the stray dogs were positive. Of 241 dogs tested, 17.4% had antibodies against Mokola virus and 5.8% against Lagos bat virus. 28.6% of human samples tested had antibodies against rabies and, of 158 human samples tested, 12 (7.5%) had antibodies against Mokola virus and 4 (2.5%) had antibodies against Lagos bat virus.

Susceptibility of laboratory animals to experimental infection with Ife virus.

The susceptibility of rabbits, domestic chickens and albino rats to experimental infection with Ife virus was investigated. Neither pyrexia nor clinical signs of disease were observed in infected rabbits or chickens. Low-grade viraemia (10(1.0) mouse lethal doses per 0.02 ml) occurred in intracerebrally (i.c.) inoculated chicks on the second day post-infection. Complement-fixing antibody was detected on the 14th day post-inoculation in rabbits and on the 7th day in chickens. Infant rats less than 3 and 5 days of age died after subcutaneous (s.c.) and i.c. inoculation, respectively; older rats survived infection. Ife virus titres were highest in the brain following both i.c. and s.c. inoculation.

Toxin-types of Clostridium perfringens strains isolated from sheep, cattle and paddock soils in Nigeria.

Two-hundred and forty-five strains of Clostridium perfringens isolated from the faeces of apparently healthy sheep and cattle and from their environments (paddock soils) in Kano and Kaduna States of Nigeria were studied. The isolates were examined by the toxin-antitoxin neutralisation tests performed intradermally in depilated albino guinea-pigs. One-hundred and twenty-seven (53.1%) of the isolates were type A, 17 (7.1%) were type B, 14 (4.9%) were type C, 44 (18.4%) were type D and 19 (7.9%) were type E. Eighteen (7.5%) were not typable while six were lost during storage. The significance of this distribution and the potential danger to animal health, especially as regards enterotoxaemias, cannot be over-emphasized.

Immunosuppression and histopathological changes in the bursa of Fabricius associated with infectious bursal disease vaccination in chicken.

The effect of the infectious bursal disease (IBD) live virus vaccine on the immune response of chicken was evaluated by the assessment of antibody response following vaccination as well as resistance to challenge with virulent virus. Birds were vaccinated at various ages and later challenged with a heterologous vaccine (NDV) or wild-type IBD virus. The BF was examined for histological changes at regular intervals. Antibody levels to NDV were monitored. Significantly higher mortality rates were observed in birds vaccinated with IBD vaccine than unvaccinated birds (P less than 0.01) following challenge, BF from vaccinated birds showed marked lymphocyte depletion and cellular infiltration with mononuclear cells. Intraocular NDV (NDV-i/o) vaccine given at day old largely prevented the immunodepressive effect of IBD vaccination on NDV vaccine. Groups that received IBD vaccine on day 14 but no NDV i/o suffered higher mortality (41.2%) and showed lower antibody response than those vaccinated on day 1 (0%) or controls which did not receive IBDV (11.8%).

The incrimination of Aedes (stegomyia) aegypti as the vector of Dirofilaria repens in Nigeria.

Six local species of culicides were identified as the common mosquitoes in Zaria, out of 15 species captured using various adult and larval collection methods. These common culicides are Culex pipiens fatigans, Anopheles gambiae grp., Mansonia africana, Culex pipiens pipiens, Aedes (stegomyia) aegypti and Aedes vittatus. They were each fed directly on a local dog naturally infected with Dirofilaria repens to evaluate their refractoriness/susceptibility to dirofilarial infection. In a number of donor-feeding trials, 39. 4% Culex pipiens fatigans; 58.9% An gambiae grp.; 60.5% Mansonia africana; 1.8% of Culex pipiens pipiens; 23.4% Ae aegypti and 3.3% of Ae vittatus successfully fed on the microfilaraemic host. Only Aedes aegypti was susceptible to the infection as all 40 (100%) Ae aegypti reaching 10-14 day post-blood meal had infective (L(3)) larvae of D. repens. The remaining five species were refractory. The microfilariae in the five non-susceptible mosquitoes were always found trapped in the blood meal in the insects midgut (stomach). These trapped microfilaria were dead by the 2nd day in the insect's midgut. However, in the susceptible Ae aegypti, the microfilariae were set free from the blood meal in the midgut and within 24h migrated to the malpighian tubules (MT) of the mosquitoes. All Ae aegypti dissected 5-7 day post-infective blood meal showed the typical quiescent sausage stage (L(2)) larvae in the malpighian tubules. At day-10 post-blood meal, relatively active infective (L(3)) larvae of D. repens were found in the MT; and by day 12-14, highly motile infective larvae had reached the insect's head and proboscis, with infective larvae occasionally oozing out during dissection through the tip of the proboscis. The rate of development of D. repens to infective larvae was faster in mosquitoes infected in July when the environmental temperature was 24.5 degrees C than those infected in November when the temperature was 22.5 degrees C. The latter were delayed for 4 days. The breeding sources of Ae aegypti, the local vector implicated were also identified. As no particular vector of this zoonotic filaria has been identified previously in Nigeria, these findings could make any control programme more focussed and easier.

Relative survival of calves in 16 traditionally managed herds in Bauchi, Nigeria.

An actuarial life-table approach was used to study the mortality of 277 calves born alive in 16 traditionally managed herds in Bauchi, Nigeria from 1993 to 1995. The proportion of calves in the herds surviving for the first 12 months was 53.8%. The probability of dying was greatest during the first month of life and decreased with age. The proportion of calves surviving in the herds has been increasing for the last 2 years. We suspect that this is probably due to improvements in management practices. Septicaemia, malnutrition and injury were the common causes of calf mortality. We recommend that more attention be given to improving the management of calves early in life in order to reduce mortality of calves and hence reduce economic losses to the herd owner.