We determined hematologic parameters of five healthy and nine sick free-ranging Lesser Flamingos (Phoeniconaias minor) from Lake Nakuru, Kenya. Heterophilia and lymphopenia were evident in sick birds, with up to 7.5-fold higher heterophil-to-lymphocyte ratio in sick birds compared to healthy birds. Leucopenia was present in a few sick birds. A higher than normal packed cell volume was observed in birds that had evidence of acute disease, whereas a lower than normal packed cell volume was seen in birds with evidence of prolonged sickness. Healthy birds had higher total white blood cell counts and lymphocyte counts and lower heterophil counts than zoo flamingos. Most sick birds were diagnosed with septicemia, occasionally with fibrinous exudation into the coelomic cavities. One bird had mycobacterial granulomas, one had a corynebacterium-associated wing abscess, and one had a wing fracture. We provide hematologic data for free-ranging Lesser Flamingos and compare the parameters of sick and healthy birds.
The Lesser Flamingo (Phoeniconaias minor) is the most abundant waterbird species in Kenya and is a major ecotourism attraction (Owino et al. 2002; Harper et al. 2003). Mass mortalities of the species are common and are associated with infectious and noninfectious causes (Kock et al. 1999; Krienitz et al. 2003; Koyo and Owino 2010). We determined hematologic parameters in healthy and sick Lesser Flamingos as part of a broader study investigating the factors responsible for mass mortality of Lesser Flamingos. The study was done with the approval of Kenya Wildlife Service, the institution responsible for wildlife research in protected areas in Kenya.
We conducted our study at Lake Nakuru, in Kenya's Rift Valley at 36°05′E, 00°24′S at an elevation of 1,754 m (Ramsar Convention 2012). We examined 14 Lesser Flamingos in March and July 2009: nine were sick and five healthy. We captured healthy birds randomly using traps (Childress and Jarrett 2005). We captured sick birds manually. We handled birds humanely to minimize stress (Fair et al. 2010) and grouped them into different age categories as described by others (Sileo et al. 1977; Zimmerman et al. 1999; Childress et al. 2005). We used the prominence of the keel muscle to score body condition (Gregory and Robins 1998).
We drew blood from the right jugular, caudal tibial, or cutaneous ulnar veins into microcollection tubes and processed it for blood cell counts (Morton et al. 1993; Campbell 2015). Blood smears were stained (Diff-Quik, American Scientific Products, McGraw Park, Illinois, USA), and our differential blood counts were based on a manual count of 300 cells (Campbell 2015). Packed cell volume (PCV) was determined using the microhematocrit method (Campbell 2015). Total white blood cell (WBC) counts were determined using the semidirect count method with phloxine B stain (Walberg 2001; Campbell 2015). The t-statistic was used to determine significant differences (α=0.05) between findings of sick and healthy birds. Age groups and sexes were treated together as no significant differences were noted among them.
The mean blood parameters of the healthy and the sick Lesser Flamingos are given in Table 1. The mean PCV of sick birds in poor body condition was significantly lower than that of the sick birds in good body condition (P=0.008). The mean WBC of sick Lesser Flamingos did not differ significantly from that of the healthy flamingos (P=0.060). The mean absolute lymphocyte count of the sick Lesser Flamingos was significantly lower than that of the healthy birds (P=0.002). The mean differential lymphocyte count of the sick Lesser Flamingos was significantly lower than that of the healthy birds (P=0.037). The mean differential lymphocyte count of the sick Lesser Flamingos in poor body condition was also significantly lower than that of the sick birds in good body condition (P=0.036). The mean differential heterophil count of sick Lesser Flamingos in poor body condition was significantly higher than that of the sick birds in good body condition (P=0.020). There were no significant differences between healthy and sick birds in the other blood parameters.
The ratio of mean differential heterophil count to mean differential lymphocyte count was fourfold higher in sick than in healthy birds. The same ratio in the sick birds in poor body condition was sixfold higher than that of the sick birds in good body condition and 7.5-fold higher than that of the healthy birds.
We compared the hematologic parameters of individual sick birds to the ranges of values from the healthy group of birds (Table 2). Heterophilia and lymphopenia were common in the sick Lesser Flamingos associated with various pathologies. Heavily granulated lymphocytes with very pale to nonstaining granules were observed in a few healthy birds. Toxic heterophils with markedly basophilic cytoplasm and occasional loss of granules were observed in one sick bird with heterophilia.
The mean PCV value we found in apparently healthy Lesser Flamingos agreed with those reported by the International Species Information System (ISIS 2013) and Peinado et al. (1992) but was lower than that reported by Hawkey et al. (1985). The range of PCV was lower than that reported by ISIS (2013) but higher than those reported by Peinado et al. (1992) and Hawkey et al. (1985). The mean WBC count we found in healthy Lesser Flamingos was higher than those previously reported, but the broad range of WBC values we found was largely in agreement (Hawkey et al. 1985; Peinado et al. 1992; ISIS 2013).
We found that the mean heterophil counts in healthy Lesser Flamingos were lower and the mean lymphocyte counts higher than previously reported values (Hawkey et al. 1985; Peinado et al. 1992; ISIS 2013). Mean lymphocyte counts were higher than mean heterophil counts in healthy Lesser Flamingos in the current study, which agreed with Peinado et al. (1992) but contrasted with others (Hawkey et al. 1985; ISIS 2013). The mean monocyte, eosinophil, and basophil counts we found in healthy Lesser Flamingos were very low, which agreed with previous reports, although the mean and range of the eosinophil count were higher than those reported previously (Hawkey et al. 1985; Peinado et al. 1992).
Our results suggested that mean WBC, lymphocyte, and eosinophil counts in healthy free-ranging Lesser Flamingos were higher and mean heterophil counts lower than those reported from zoo birds (Hawkey et al. 1985; Peinado et al. 1992). Our results also suggested that WBC counts are highly variable in free-ranging Lesser Flamingos, just like in those raised in zoos (Hawkey et al. 1985; Peinado et al. 1992). Our data further suggested that mean PCV in free-ranging Lesser Flamingos was comparable to that of birds in zoos, although it is variable in both groups of birds. The numbers of birds that we studied and those studied by others were small; thus, the observed differences should be interpreted cautiously (Hawkey et al. 1985; Peinado et al. 1992). The methods and the conditions in studies differed widely and could contribute to the observed differences. The range of sampling dates in our study could also have affected our results.
Our results indicated that lymphopenia and heterophilia were consistent changes in the blood of most sick birds, although leucopenia was also evident in some of the birds. The relative eosinophilia in some sick birds in good body condition was possibly due to marked lymphopenia. Most of the sick birds in poor body condition had normocytic, normochromic anemia, possibly due to chronic disease. A few of the sick birds in good body condition had evidence of hemoconcentration, possibly due to dehydration. The differences in blood parameters between sick birds in good body condition and those in poor body condition reflect the progressive nature of blood changes in sick birds. Our findings show that hematology is a useful indicator of the health status in free-ranging Lesser Flamingos, in agreement with the findings of Hawkey et al. (1985) for captive birds.
We acknowledge the directors of the Kenya Wildlife Service, the Directorate of Veterinary Services, and the National Museums of Kenya for support; F. M. Mukendi, Head of Nakuru Veterinary Investigation Laboratory, for allowing us to use the lab; William Kimosop and James Kimaru (Lake Bogoria National Reserve); John Kariuki, Everlyn Silali, James Mungai, Edward Kingori, Philip Imbusi, and Fred Omengo (Kenya Wildlife Service); Muchai Muchane, Peter Njoroge, Wanyoike Wamiti, and Onesmus Kioko (National Museums of Kenya); John Mukiri, Ezekiel Weda, John Mwongi Kinyuru, David Muriithi, Richard Otieno, Zacharia Munene, Anne Munene, and Edith Keya (Department of Veterinary Pathology, Microbiology and Parasitology, University of Nairobi); Waweru Ngatia (Nakuru Water Services Company); Mercy Olivia (White Oak Foundation); and Val Beasley (University of Illinois at Urbana-Champaign), whose ideas during the transdisciplinary symposium on recent Lesser Flamingo mortality conducted in 2004 inspired the study.
Deceased 1 February 2013